MDP_RUL_0002_04A

Market Rules
Chapter 4
Grid Connection
Requirements -
Appendices

Public Issue Date: March 5, 2025

Library Record No. MDP_RUL_0002_04A
Document Name Market Rules for the Ontario Electricity Market
Issue Issue 16.0
Reason for Issue Baseline 53.0
Effective Date March 5, 2025
Market Rules for the Ontario Electricity Market Document Change History

Document Change History

Issue/Draft Reason for Issue Date
Issue 1.0 Baseline 8.0 September 25, 2002
Issue 2.0 Baseline 10.0 September 10, 2003
Issue 3.0 Baseline 12.1 December 8, 2004
Issue 4.0 Baseline 14.0 September 14, 2005
Issue 5.0 Baseline 16.0 September 13, 2006
Issue 6.0 Effective date for MR-00359 March 6, 2010
Issue 7.0 Baseline 23.1 June 2, 2010
Issue 8.0 Baseline 27.1 June 6, 2012
Issue 9.0 Baseline 29.0 March 6, 2013
Issue 10.0 Baseline 29.1 June 5, 2013
Issue 11.0 Baseline 33.1 June 3, 2015
Issue 12.0 Baseline 34.0 September 9, 2015
Issue 13.0 Baseline 44.1 December 2, 2020
Issue 14.0 Baseline 45.0 February 26, 2021
Issue 15.0 Baseline 46.1 December 1, 2021
Issue 16.0 Baseline 53.0 March 5, 2025

Related Documents
Library Record No. Document Title Version
MDP_RUL_0002 Market Rules for the Ontario 88.0
Electricity Market

Issue 16.0 - March 5, 2025 Public

Document Control Market Rules for the Ontario Electricity Market

Document Control

Authorities
Prepared by
Market Rules

Reviewed by
Technical Panel
Legal Affairs

Approved by
IESO Board

Distribution List
Name Organization

Public Issue 16.0 - March 5, 2025

Market Rules for the Ontario Electricity Market

Table of Contents
Table of Contents

4
Appendix 4.1 – IESO-Controlled Grid Performance Standards ...................... 1

Appendix 4.2 – Requirements for Generation and Electricity Storage Facilities

Connected to the IESO-Controlled Grid.................................................... 2

Appendix 4.3 – Requirements for Connected Wholesale Customers and

Distributors Connected to the IESO-Controlled Grid .............................. 5

Appendix 4.4 – Transmitter Requirements ....................................................... 7

Appendix 4.5 – [Intentionally left blank] ........................................................... 8

Appendix 4.5A – [Intentionally left blank] ......................................................... 9

Appendix 4.6 – [Intentionally left blank] ......................................................... 10

Appendix 4.7 – [Intentionally left blank] ......................................................... 11

Appendix 4.8 – [Intentionally left blank] ......................................................... 12

Appendix 4.9 – [Intentionally left blank] ......................................................... 13

Appendix 4.10 – [Intentionally left blank] ....................................................... 14

Appendix 4.11 – [Intentionally left blank] ....................................................... 15

Appendix 4.12 – [Intentionally left blank] ....................................................... 16

Appendix 4.13 – [Intentionally left blank] ....................................................... 17

Appendix 4.14 – [Intentionally left blank] ....................................................... 18

Appendix 4.15 – IESO Monitoring Requirements: Generators...................... 19

Appendix 4.16 – IESO Monitoring Requirements: Transmitters ................... 24

Appendix 4.17 – IESO Monitoring Requirements: Connected Wholesale

Customers and Distributors .................................................................... 28

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4 Table of Contents

Appendix 4.18 – IESO Monitoring Requirements: Embedded Load Consumers

MDP_RUL_0002_04A

.................................................................................................................... 31

Appendix 4.19 – IESO Monitoring Requirements: Generator Performance

Standards .................................................................................................. 32

Appendix 4.20 – IESO Monitoring Requirements: Transmitter Performance

Standards .................................................................................................. 34

Appendix 4.21 – IESO Monitoring Requirements: Transmitter Performance

Standards .................................................................................................. 35

Appendix 4.22 – IESO Monitoring Requirements: Distributors and Connected

Wholesale Customer Performance Standards ....................................... 36

Appendix 4.23 – IESO Monitoring Requirements: Embedded Load Consumers

Performance Standards ........................................................................... 37

Appendix 4.24 – IESO Monitoring Requirements: Electricity Storage

Participants ............................................................................................... 38

Appendix 4.25 – IESO Monitoring Requirements: Electricity Storage

Performance Standards ........................................................................... 44

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Market Rules for the Ontario Electricity Market

Appendix 4.1 – IESO-Controlled Grid

Performance Standards
Grid Connection Requirements - Appendices

4
Ref Item Requirement
Transmission System
1 Frequency variations All equipment shall be capable of continuously operating in the range
between 59.5 Hz and 60.5 Hz.
2 Voltage variations Under normal conditions voltages are maintained within the range below.

Transmission Voltage:
Nominal (kV) 500 230 115
Maximum Continuous (kV) 550 250* 127*
Minimum Continuous (kV) 490 220 113

*In northern Ontario, the maximum continuous voltage for the 230 and 115
kV systems can be as high as 260 kV and 132 kV respectively
3 [Intentionally left blank]
4 [Intentionally left blank]
5 [Intentionally left blank]
6 [Intentionally left blank]
7 [Intentionally left blank]
8 [Intentionally left blank]

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4 Grid Connection Requirements - Appendices

Appendix 4.2 – Requirements for

Generation and Electricity Storage
MDP_RUL_0002_04A

Facilities Connected to the IESO-

Controlled Grid
The performance requirements set out below shall apply to generation facilities subject to a
connection assessment finalized after September 21, 2020. Performance of alternative
technologies shall be comparable with that of conforming conventional synchronous
generation with an equal apparent power rating.

These performance requirements shall also apply to electricity storage units at all
times while connected to the IESO-controlled grid, unless the IESO identifies specific
performance requirements that are not applicable to an electricity storage unit for those with
a connection assessment finalized after January 18, 2021. Due consideration will be given to
inherent limitations.

Each facility that was authorized to connect to the IESO-controlled grid prior to September
21, 2020 shall remain subject to the performance requirements in effect for each associated
system at the time its authorization to connect to the IESO-controlled grid was granted or
agreed to by the market participant and the IESO (i.e. the “original performance
requirements”). These original performance requirements shall prevail until the main
elements of an associated system (e.g. governor control mechanism, main exciter, power
inverter) are replaced or substantially modified. At that time, the associated system that is
replaced or substantially modified shall meet the applicable performance requirements
detailed below. All other systems, not affected by replacement or substantial modification,
shall remain subject to the original performance requirements.

Appendix 4.2–2 Public Issue 16.0 - March 5, 2025

Market Rules for the Ontario Electricity Market

Category
1. Off-Nominal Frequency
Operation
Grid Connection Requirements - Appendices

Generation facilities or electricity storage facilities directly connected to the IESO-

controlled grid shall have the capability to:
Operate continuously between 59.4 Hz and 60.6 Hz and for a limited period of time in the region
4
bounded by straight lines on a log-linear scale defined by the points (0.0 s, 57.0 Hz), (3.3 s, 57.0 Hz), and
(300 s, 59.0 Hz) and the straight lines on a log-linear scale defined by the points (0.0 s, 61.8 Hz), (8 s, 61.8
Hz), and (600 s, 60.6 Hz).
2. Speed/Frequency Regulate speed/frequency with an average droop based on maximum active power adjustable between
Regulation 3% and 7% and set at 4% unless otherwise specified by the IESO. Regulation deadband shall not be wider
than ±0.06%. Speed/frequency shall be controlled in a stable fashion in both interconnected and island
operation. A sustained 9% change of applicable rated active power as defined in category 4 after 10 s in
response to a step change of speed of 0.5% during interconnected operation shall be achievable. Due
consideration will be given to inherent limitations such as mill points and gate limits when evaluating
active power changes. Control systems that inhibit primary frequency response shall not be enabled
without IESO approval.
3. Voltage Ride-Through Ride through routine switching events and design criteria contingencies assuming standard fault
detection, auxiliary relaying, communication, and rated breaker interrupting times unless disconnected
by configuration. For Inverter-based units, momentary current cessation or reduction of output current
during system disturbances is not permitted without IESO approval.
4. Active Power Continuously supply all levels of active power output within a +/- 5% range of its rated terminal
voltage. Rated active power is the smaller output at either rated ambient conditions (e.g. temperature,
head, wind speed, solar radiation) or 90% of rated apparent power. For electricity storage facilities, rated
active power values shall be separately specified for both injection and withdrawal operations. To satisfy
steady-state reactive power requirements, active power reductions to rated active power are permitted.
5. Reactive Power Continuously (i.e., dynamically) inject or withdraw reactive power at the high-voltage terminal of the
main output transformer 1 up to 33% of the applicable rated active power at all levels of active power,
and at the typical transmission system voltage, except where a lesser continually available capability is
permitted with the IESO’s approval. A conventional synchronous unit with a power factor range of 0.90
lagging and 0.95 leading at rated active power connected via a main output transformer impedance not
greater than 13% based on generation unit rated apparent power is acceptable. Reactive power losses or
charging between the high-voltage terminal of the main output transformer and the connection point
shall be addressed in a manner permitted by IESO approval.
6. Automatic Voltage Regulate voltage automatically within ±0.5% of any setpoint within ±5% of rated voltage at the low-
Regulator (AVR) voltage terminal of the main output transformer if the transformer impedance is not more than 13%
based on the rated apparent power of the generation facility or electricity storage facility or at a point
approved by the IESO. Reactive power-voltage droop or AVR reference load current compensation shall
not be enabled without IESO approval. The equivalent time constants shall not be longer than 20 ms for
voltage sensing and 10 ms for the forward path to the exciter output.
7. Excitation System for Provide (a) Positive and negative ceilings not less than 200% and 140% of rated field voltage,
Synchronous Machines respectively, while supplying the field winding of the generation unit or electricity storage unit operating
Greater than 20 MVA or at nominal voltage under open circuit conditions; (b) An excitation transformer impedance not greater
any Synchronous Machines than 10% on excitation system base; (c) A voltage response time to either ceiling not more than 50 ms for
within Facilities Greater a 5% step change from rated voltage under open-circuit conditions; and (d) A linear response between
than 75 MVA ceilings.

8. Power System Stabilizer Provide (a) A change of power and speed input configuration; (b) Positive and negative output limits not
(PSS) for Synchronous less than ±5% of rated AVR voltage; (c) Phase compensation adjustable to limit angle error to within 30°
Machines within Facilities between 0.2 Hz and 2.0 Hz under conditions specified by the IESO, and (d) Gain adjustable up to an
Greater than 75 MVA amount that either increases damping ratio above 0.1 or elicits poorly damped exciter modes of
oscillation at maximum active output unless otherwise specified by the IESO. Due consideration will be
given to inherent limitations.
For electricity storage units, Power System Stabilizer shall be disabled while withdrawing.
9. Phase Unbalance Provide an open circuit phase voltage unbalance not more than 1% and operate continuously with a
phase voltage unbalance as high as 2% at the high-voltage terminal of its main output transformer.
10. Armature and Field Provide short-time capabilities specified in IEEE/ANSI 50.13 and continuous capability determined by
Limiters either maximum field current, maximum stator current, core-end heating, or minimum field
current. More restrictive limiting functions, such as steady state stability limiters, shall not be enabled
without IESO approval.

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4 Grid Connection Requirements - Appendices

11. Technical
Characteristics
MDP_RUL_0002_04A

Exhibit, at the high-voltage terminal of its main output transformer, performance comparable to an
equivalent synchronous generation unit with characteristic parameters within typical ranges. Inertia,
unsaturated transient impedance, transient time constants, and saturation coefficients shall be within
typical ranges (e.g. H > 1.2 Aero-derivative, H > 1.2 Hydroelectric units less than 20 MVA, H > 2.0
Hydroelectric units 20 MVA or larger, H > 4.0 Other synchronous units, X’d < 0.5, T’d0 > 2.0, and S1.2 <
0.5) except where permitted by IESO approval.
12. Reactive Power For a constant voltage at the high-voltage terminal of the main output transformer, achieve a sustained
Response to Voltage reactive power change of 30% of generation facility or electricity storage facility rated apparent power at
Changes of Inverter-Based the low-voltage terminal of the main output transformer within 3s following a step change no larger than
Units 4% to the AVR voltage reference. AVR response to the voltage error signal must be consistent over the
entire operating range.

1
A main output transformer steps up the voltage from the generation unit/facility to the transmission voltage level.

Appendix 4.2–4 Public Issue 16.0 - March 5, 2025

Market Rules for the Ontario Electricity Market

Appendix 4.3 – Requirements for

Connected Wholesale Customers and
Grid Connection Requirements - Appendices

4
Distributors Connected to the IESO-
Controlled Grid
The performance requirements set out below shall apply to connected wholesale customers
and distributors that are connecting equipment or facilities to the IESO-controlled grid or to
their distribution systems after January 18, 2021.

Equipment connected within a connected wholesale customer’s or distributor’s facilities or

distribution systems that was authorized to connect prior to January 18, 2021 shall remain
subject to the performance requirements in effect at the time its authorization to connect was
granted (i.e. the “original performance requirements”). These original performance
requirements shall prevail until the main elements of an associated system are replaced or
substantially modified. At that time, the associated system that is replaced or substantially
modified shall meet the applicable performance requirements detailed below. All other
systems not affected by replacement or substantial modification, shall remain subject to the
original performance requirements.

Category Requirement
1. Power Factor Connected wholesale customers and distributors connected to the IESO-controlled grid shall operate at a
power factor within the range of 0.9 lagging to 0.9 leading as measured at the defined meter point.

2. Under Frequency Load Connected wholesale customers and distributors connected to the IESO-controlled grid may be required to
Shedding participate in under frequency load shedding
3. Remedial Action Schemes Connected wholesale customers and distributors connected to the IESO-controlled grid may be required to
participate in remedial action schemes.

4. Voltage Reduction Distributors connected to the IESO-controlled grid with directly connected load facilities of aggregated
rating above 20 MVA and with the capability to regulate distribution voltages under load, shall install and
maintain facilities and equipment to provide voltage reduction capability.
5. [Intentionally left blank]
6. [Intentionally left blank]
7. [Intentionally left blank]
8. [Intentionally left blank]
9. Testing and Compliance Connected wholesale customers and distributors connected to the IESO-controlled grid shall test and
Monitoring maintain their equipment in accordance with all applicable reliability standards.
10. Metering Connected wholesale customers and distributors connected to the IESO-controlled grid shall comply with
metering codes and standards set by the IESO.
11. Voltage Ride-Through Equipment connected within a connected wholesale customer’s or a distributor’s facility or distribution
system that is connected to the IESO-controlled grid shall ride through routine switching events and
design criteria contingencies on the transmission system assuming standard fault detection, auxiliary
relaying, communication, and rated breaker interrupting times unless either disconnected by
configuration or a failure to do so has been assessed and confirmed by the IESO as having no material
adverse effect on the operation of the IESO-controlled grid.

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4 Grid Connection Requirements - Appendices

12. Generation Units and

Electricity Storage Units
MDP_RUL_0002_04A

Any generation unit or electricity storage unit connected within a connected wholesale customer’s or a
distributor’s facility or distribution system that is connected to the IESO-controlled grid shall meet, at a
minimum, the performance requirements for Off-Nominal Frequency Operation (category 1),
Speed/Frequency Regulation (category 2), and Voltage Ride-Through (category 3) specified in Appendix
4.2.
If a connected wholesale customer injects active power into the IESO-controlled grid, all performance
requirements specified in Appendix 4.2 are applicable to the generation units and electricity storage units
installed within their facility.

Note: These performance requirements shall apply to electricity storage units and generation units at all
times while connected within a connected wholesale customer’s or distributor’s facilities or distribution
system that is connected to the IESO-controlled grid, unless the IESO identifies specific performance
requirements that are not applicable to an electricity storage unit or generation unit for those with a
connection assessment finalized after January 18, 2021. Due consideration will be given to inherent
limitations.

Appendix 4.3–6 Public Issue 16.0 - March 5, 2025

Market Rules for the Ontario Electricity Market

Appendix 4.4 – Transmitter Requirements

Ref
1
Item
Abrupt Voltage
Requirement
Grid Connection Requirements - Appendices

Voltage changes shall not normally exceed 4% of steady state rms for capacitor switching
4
Changes operations. Voltage changes shall not normally exceed 10% of steady state rms for line switching
operations
2 Frequency All equipment shall be capable of continuous operation within the range of 59.5 to 60.5 Hz and
Variations have the capability to operate for 10 minutes in the range 58 to 61.5 Hz.
3 Load Shedding Each transmitter shall comply with IESO requirements for automatic under-frequency load
Facilities shedding in accordance with its operating agreement. Each transmitter shall be able to manually
drop up to 50% of its load within 10 minutes.
4 Automatic Reclosure Transmission circuits shall be equipped with timed, single-shot automatic re-closing facilities.
Reclosure shall only be initiated by protections that operate when it is highly likely that the fault is
not permanent. Reclosure within 5 seconds of fault detection is allowed only in exceptional
circumstances. Angle supervision shall be provided on all breakers rated at 230 kV and above.
Automatic reclosure shall remain enabled only for a limited period of time, usually about 40
seconds, following initiation.
5 Thermal Ratings • Market participants that own and operate transmission equipment shall provide the IESO
with the continuous and limited time thermal ratings for their transmission circuits and
transformers.
• Market participants shall provide this information to the IESO via a data link with a minimum
update rate of 5 minutes or as agreed to by the IESO. For backup and pre-dispatch
purposes, market participants shall provide a thermal rating table in a suitable format to
facilitate IESO applications to perform thermal rating interpolation.
• Where other equipment (e.g. wavetraps) is more limiting, market participants shall provide
the IESO with the thermal rating of the most restrictive element.
• Generators and connected wholesale customers that own and operate transmission
equipment that is part of the IESO-controlled grid shall provide the IESO with the continuous
and limited time thermal ratings for their transmission circuits and transformers only if
required by the IESO to maintain reliable operation of the IESO-controlled grid.
• Limited time thermal ratings shall be 15-minute ratings, unless mutually agreed by the IESO
and market participant.
6 Protective System Protection systems shall be constructed and maintained in accordance with all applicable
Requirements reliability standards.
7 IESO Information The transmitter shall provide any information that the IESO deems necessary to direct the
Requirements operation of the IESO-controlled grid. This Information, including, but not limited to, voltages,
flows, and equipment status shall be telemetered continually to the IESO.
8 Voltage Reduction Transmitters with the ability to regulate distribution voltages under load shall install and maintain
facilities and equipment to provide voltage reduction capability.
9 Telecommunications Communication channels shall have a level of reliability that is consistent with the required
performance of the associated protection system. Telecommunications shall be designed to
assure adequate signal transmission during transmission disturbances and may be provided with
means to verify proper signal performance. Equipment may be monitored to assess its readiness
and be powered by batteries or other sources independent of the IESO.
10 Testing and Transmitters shall test and maintain their equipment in accordance with all applicable reliability
Compliance standards.
Monitoring
11 Metering Transmitters shall comply with the metering codes and standards set by the IESO.

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4 Grid Connection Requirements - Appendices

Appendix 4.5 – [Intentionally left blank]

MDP_RUL_0002_04A

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Market Rules for the Ontario Electricity Market

Appendix 4.5A – [Intentionally left blank]

Grid Connection Requirements - Appendices

Issue 16.0 - March 5, 2025 Public Appendix 4.5–9

4 Grid Connection Requirements - Appendices

Appendix 4.6 – [Intentionally left blank]

MDP_RUL_0002_04A

Issue 16.0 - March 5, 2025 Public Appendix 4.6–10

Market Rules for the Ontario Electricity Market

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Grid Connection Requirements - Appendices

Issue 16.0 - March 5, 2025 Public Appendix 4.7–11

4 Grid Connection Requirements - Appendices

Appendix 4.8 – [Intentionally left blank]

MDP_RUL_0002_04A

Appendix 4.8–12 Public Issue 16.0 - March 5, 2025

Market Rules for the Ontario Electricity Market

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Grid Connection Requirements - Appendices

Issue 16.0 - March 5, 2025 Public Appendix 4.9–13

4 Grid Connection Requirements - Appendices

Appendix 4.10 – [Intentionally left blank]

MDP_RUL_0002_04A

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Market Rules for the Ontario Electricity Market

Appendix 4.11 – [Intentionally left blank]

Grid Connection Requirements - Appendices

Issue 16.0 - March 5, 2025 Public Appendix 4.11–15

4 Grid Connection Requirements - Appendices

Appendix 4.12 – [Intentionally left blank]

MDP_RUL_0002_04A

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Market Rules for the Ontario Electricity Market

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Grid Connection Requirements - Appendices

Issue 16.0 - March 5, 2025 Public Appendix 4.13–17

4 Grid Connection Requirements - Appendices

Appendix 4.14 – [Intentionally left blank]

MDP_RUL_0002_04A

Appendix 4.14–18 Public Issue 16.0 - March 5, 2025

Market Rules for the Ontario Electricity Market

Appendix 4.15 – IESO Monitoring

Requirements: Generators
Grid Connection Requirements - Appendices

4
The following information, as a minimum, shall be available on a continual basis to the IESO
from:

(a) any generator (i) whose generation facility is connected to the IESO-controlled grid, or
(ii) that is participating in the IESO-administered markets; and

(b) any embedded generator (i) that is not a market participant or whose embedded
generation facility is not a registered facility; (ii) whose embedded generation facility
includes a generation unit rated at greater than 20 MVA or that comprises generation units
the ratings of which in the aggregate exceeds 20 MVA; and (iii) that is designated by the
IESO for the purposes of section 7.3.1 of this Chapter as being required to provide such data
in order to enable the IESO to maintain the reliability of the IESO-controlled grid.

TYPE INFORMATION REQUIREMENTS

Major generation Monitored Quantities

facility
1. Active Power (MW) and Reactive Power (MX)
a) The standard requirement for active and reactive power is the provision of net MW and net MX
or gross MX. Gross MW and gross MX or net MX are also to be provided, if designated by the
IESO as required for:
(i) determination of operating security limits;
(ii) to maintain reliable operation of the IESO-controlled grid;
(iii) for compliance monitoring purposes; or
(iv) if provision of only the standard requirement values as defined above would have a negative
impact on other market participants through reduced operating security limits.
b) For generation units rated greater than or equal to 100 MVA, the standard requirement as
defined in part a) for each generation unit shall be provided, and gross MW and gross MX or net
MX for each generation unit shall be provided if designated by the IESO as required using the
criteria listed above in part a).
c) For generation units rated at less than 100 MVA:
(i) for a group of generation units if those generation units are similar in size and operating
characteristics, the standard requirement as defined in part a) shall be provided as a total for
these generation units, and total gross MW and gross MX or net MX shall be provided if
designated by the IESO as required using the criteria listed above in part a); or
(ii) if designated by the IESO as required for determination of operating security limits or to
maintain reliable operation of the IESO-controlled grid or for compliance monitoring purposes,
the standard requirement as defined in part a) for each generating unit shall be provided, and
gross MW and gross MX or net MX for each generation unit shall be provided if designated by
the IESO as required using the criteria listed above in part a).
d) For generation facilities that have been aggregated pursuant to Chapter 7 section 2.3:

Issue 16.0 - March 5, 2025 Public Appendix 4.15–19

4 Grid Connection Requirements - Appendices

TYPE INFORMATION REQUIREMENTS

MDP_RUL_0002_04A

(i) the standard requirement as defined in part a) shall be provided as an aggregated total, and
an aggregated total gross MW and gross MX or net MX shall be provided if designated by the
IESO as required using the criteria listed above in part a); or
(ii) if so designated by the IESO as required for determination of operating security limits or to
maintain reliable operation of the IESO-controlled grid or for dispatch compliance monitoring
purposes, the standard requirement as defined in part a) for each generating unit shall be
provided, and gross MW and gross MX or net MX for each generation unit shall be provided if
designated by the IESO as required using the criteria listed above in part a).
e) For frequency changers:
(i) total MW and MX at either frequency; or
(ii) if so designated by the IESO as required for determination of operating security limits, total
MW and MX at both frequencies.
f) For synchronous condensers:
(i) total MX.

2. Voltage:
a) For each generation unit, unit terminal voltage, except if generation units are connected to a
common low voltage bus section, then the bus section voltage is adequate for those generation
units.

3. Frequency:
a) For each generation unit or generation facility providing black start capability, frequency of the
applicable generation unit or generation facility.

4. Equipment Status
a) Unit mode (i.e. generator, condenser, pump) for each generation unit capable of different modes
of operation.
b) AGC status for each generation unit providing regulation.
c) AVR and Stabilizer Status for each generating unit with a rated capacity > 100 MVA. Stabilizer
status reporting is only required if it can be switched off by generation facility personnel remotely
or at the facility.
d) AVR and Stabilizer status for each generation unit with a rated capacity < 100 MVA if the status
of this equipment is designated by the IESO as required for determination of operating security
limits or to maintain reliable operation of the IESO-controlled grid. Stabilizer status reporting is
only required if it can be switched on or off by market participant operating personnel remotely
or at the facility.
e) Synchronizing Breaker status for each generation unit. Where a generation facility is designed
such that no low voltage synchronizing breaker is installed for each generation unit, the status of
the appropriate HV breaker(s) and disconnect switch(es) normally used to isolate the generation
unit must be provided. Where this results in access to the majority of breakers on a bus, the
status of the remainder of the breakers shall be provided to complete the bus configuration.
Where a generation facility is designed such that there are disconnect switches in parallel, or
directly in series, with the synchronizing breaker, the status of those switches is also required.
f) Remedial Action Scheme status for each applicable generation unit.

Significant Monitored Quantities

generation facility
and minor 1. Active Power (MW) and Reactive Power (MX):
generation facility

Appendix 4.15–20 Public Issue 16.0 - March 5, 2025

Market Rules for the Ontario Electricity Market

TYPE

connected to IESO-
controlled grid
Grid Connection Requirements - Appendices

INFORMATION REQUIREMENTS

a) The standard requirement for active and reactive power is the provision of net MW
and net MX or gross MX. Gross MW and gross MX or net MX are also to be
provided, if designated by the IESO as required for:
4
(i) determination of operating security limits;
(ii) to maintain reliable operation of the IESO-controlled grid;
(iii) for compliance monitoring purposes; or
(iv) if provision of only the standard requirement values as defined above would have a
negative impact on other market participants through reduced operating security
limits.
b) For generation facilities that have not been aggregated pursuant to Chapter 7 section
2.3:
(i) for a group of generation units if those generation units are similar in size and
operating characteristics, the standard requirement as defined in part a) shall be
provided as a total for these generation units, and total gross MW and gross MX or
net MX shall be provided if designated by the IESO as required using the criteria
listed above in part a);
(ii) if designated by the IESO as required for determination of operating security limits
or to maintain reliable operation of the IESO-controlled grid or for compliance
monitoring purposes, the standard requirement as defined in part a) for each
generating unit shall be provided, and gross MW and gross MX or net MX for each
generation unit shall be provided if designated by the IESO as required using the
criteria listed above in part a).
c) For generation facilities that have been aggregated pursuant to Chapter 7 section 2.3:
(i) the standard requirement as defined in part a) shall be provided as an aggregated
total, and an aggregated total gross MW and gross MX or net MX shall be provided
if designated by the IESO as required using the criteria listed above in part a); or
(ii) if so designated by the IESO as required for determination of operating security
limits or to maintain reliable operation of the IESO-controlled grid or for dispatch
compliance monitoring purposes, the standard requirement as defined in part a) for
each generating unit shall be provided, and gross MW and gross MX or net MX for
each generation unit shall be provided if designated by the IESO as required using
the criteria listed above in part a).
d) For frequency changers:
(i) total MW and MX at either frequency; or
(ii) if so designated by the IESO as required for determination of operating security
limits, total MW and MX at both frequencies.
e) For Synchronous Condensers:
(i) Total MX.
2. Voltage:
a) For generation units that are VAR dispatchable, unit terminal voltage, except if the
generation units are connected to a common low voltage bus section, then the bus
section voltage is adequate for those generation units.
3. Frequency:

Issue 16.0 - March 5, 2025 Public Appendix 4.15–21

4 Grid Connection Requirements - Appendices

TYPE INFORMATION REQUIREMENTS

MDP_RUL_0002_04A

a) For each generation unit or generation facility providing black start capability,
frequency of the applicable generation unit or facility.
4. Equipment Status
a) Unit mode (i.e. generator, condenser, pump) for each generation unit capable of
different modes of operation.
b) AVR and Stabilizer Status for each generation unit if the status of this equipment is
designated by the IESO as required for determination of operating security limits or to
maintain reliable operation of the IESO-controlled grid. Stabilizer status reporting is
only required if it can be switched on or off by market participant operating personnel
remotely or at the facility.
c) Synchronizing Breaker Status for each generation unit. Where a generation facility is
designed such that no low voltage synchronizing breaker is installed for each
generation unit, the status of the appropriate HV breaker(s) and disconnect switch(es)
normally used to isolate the generation unit must be provided. Where this results in
access to the majority of breakers on a bus, the status of the remainder of the
breakers shall be provided to complete the bus configuration.
Where a generation facility is designed such that there are disconnect switches in
parallel, or directly in series, with the synchronizing breaker, the status of those
switches is also required.
d) Remedial Action Scheme status for each applicable generation unit.
Self-scheduling None
generation facility
with a name-plate
rating of less than
10 MW
Intermittent and • if a major generation facility, as described above for a major generation facility
transitional
scheduling • if a significant generation facility, as described above for a significant generation facility
generator • if a minor generation facility, as described above for a minor generation facility if
designated by the IESO at the time of registration as affecting the reliability of the IESO-
controlled grid
• if a small generation facility, none
Small generation None
facility
Minor generation • Total active power (MW) output of the individual generation unit or of the aggregated
facility that is resource.
embedded in a
distribution system • Unit status if the facility is comprised of a single generation unit.
and registered as a • Aggregated resource status if the facility is comprised of aggregated resources, i.e. if at
dispatchable least one unit of the aggregated resource is synchronized, the aggregated resource is
generator synchronized or if no unit in the aggregated resource is synchronized, the aggregated
resource is not synchronized.
• Reactive Power (MX) output, if requested by the IESO for reliable operation of the IESO-
controlled grid, of individual generation units or of the aggregated resource.

Appendix 4.15–22 Public Issue 16.0 - March 5, 2025

Market Rules for the Ontario Electricity Market

TYPE

Generation facility
Grid Connection Requirements - Appendices

SYNCHROPHASOR DATA REQUIREMENTS

The following are required unless otherwise specified by the IESO:

4
1. For generation units rated greater than or equal to 100 MVA (name-plate rating), each
generation unit shall provide positive sequence voltage phasor, positive sequence
current phasor and frequency from generator terminal.
2. For generation units connected to the IESO-controlled grid through a common
connection point, whose aggregated rated size is greater than or equal to 100 MVA
(aggregate name-plate rating), positive sequence voltage phasor, aggregated positive
sequence current phasor and frequency shall be provided from the generation facility
side of the connection point to the grid.
3. For generation units, regardless of rated size, whose output power flow is a part of an
Interconnection Reliability Operating Limit (IROL) definition, positive sequence voltage
phasor, positive sequence current phasor and frequency shall be provided at the
terminals defining the IROL.
Unless otherwise specified by the IESO, synchrophasor data requirements shall comply with the
corresponding Market Manual.

Issue 16.0 - March 5, 2025 Public Appendix 4.15–23

4 Grid Connection Requirements - Appendices

Appendix 4.16 – IESO Monitoring

Requirements: Transmitters
MDP_RUL_0002_04A

The following information regarding the IESO-controlled grid, as a minimum, shall be

available on a continual basis to the IESO from transmitters. Needs of the state estimation
process or other reasons may result in additional requirements. The direction of all real and
reactive power flows shall be indicated measurements.
Equipment Type Voltage Monitored Status Monitored Quantities
Level
Station Bus
Specified phase-phase and phase to
ground voltages measured at different
buses.
50 kV and
Bus Voltage
higher Note: a line voltage may be used if bus
PTs are not available.

As directed by the IESO for points on

the IESO-controlled grid that are
50 kV and significant for reliability purposes. High
Frequency
higher accuracy PTs & measurements of
frequency are required at a number of
stations at the discretion of the IESO.
TRANSFORMATIO
N
Isolating switches Megawatts and Megavars for the high
voltage winding for each transformer
As described in the “Reactive
Devices” section below for ancillary Megawatts and Megavars for the low
equipment associated with the voltage winding for each transformer, if
transformer other than station service is connected
50 kV and to the tertiary winding.
Autotransformers
above

ULTC tap positions for the transformer

The IESO may require the monitoring of
any Off-Load Tap Changer positions.
Voltage, MW and MVAR may be
Phase Shifting required as directed by the IESO
Transformers 50 kV and Bypass and isolating
higher switches
All transformer tap positions

Appendix 4.16–24 Public Issue 16.0 - March 5, 2025

Market Rules for the Ontario Electricity Market

Equipment Type Voltage

Level
Monitored Status

Bypass and isolating switches

Grid Connection Requirements - Appendices

Monitored Quantities

MW and MVAR
4
Phase to ground Voltage, for each
winding measured on the high voltage
Step Down 50 kV and
side. Where only LV PTs are available:
Transformers higher
MW and phase to phase voltages for
each LV winding
ULTC tap positions.
MW and MVAR may be required as
directed by the IESO
Bypass and isolating switches
Voltage Regulating 50 kV and
Transformers higher ULTC tap positions for the transformer
The IESO may require the monitoring of
any Off-Load Tap Changers.
Isolating Devices
All Circuit breakers, including bus
tie breakers
All breakers connecting loads for
each tertiary winding of
autotransformer other than that for
Station Service

50 kV and Each capacitor breaker

higher All line disconnect switches
including
connected All transformer disconnect and by-
tertiaries pass switches
All bus sectionalizing switches

Breakers and All isolating switches for reactors

Switches and capacitors where circuit
breakers are not provided
All in line switches as specified
Note: The status of breaker
isolating switches is not required

Breakers of Low Voltage

Capacitors, Reactors,
Transformers that are part of or
have an impact on the IESO-
controlled grid or that are subject to
Below 50 kV a contracted ancillary services
contract including by means or
within the scope of an operating
agreement
Each reactor or condensor breaker.

Issue 16.0 - March 5, 2025 Public Appendix 4.16–25

4 Grid Connection Requirements - Appendices

Equipment Type

Isolating and by-

Voltage
Level

50 kV and
Monitored Status

Isolating and bypass switches for

each transformer
MDP_RUL_0002_04A

Monitored Quantities

pass switches higher Bus sectionalizing switches

Reactor and capacitor isolation

Circuits

Circuit forming part MW and MVAR line flow at each

50 kV and terminal
of the IESO-
higher
controlled grid

• MW and MVAR line flow

Circuit that is an
interconnection with 50 kV and • (MW from the billing meter point)
another control higher where practical
area

Special Protection
Schemes
As directed by the IESO on a case- As directed by the IESO on a case-by-
by-case basis. Where so directed, case basis.
Remedial Action 50 kV and must include all associated
Schemes (RAS) higher capacitors and reactors breaker
status.

Reactive Devices
All levels Breaker Status MVARs where output is variable.
Capacitors,
designated by
Synchronous
the IESO as
Condensors,
affecting the
Reactors, Static Var
reliability of
Compensators,
the IESO-
FACTS
controlled grid

Appendix 4.16–26 Public Issue 16.0 - March 5, 2025

Market Rules for the Ontario Electricity Market

Equipment Type

Station Buses
Voltage
Level
50 kv and
higher
Grid Connection Requirements - Appendices

Monitored Syncrophasor Quantities

Positive sequence voltage phasor magnitude

Positive sequence voltage phasor angle
4
(a) 500 kV station

(b) Bulk Power

System (BPS) Frequency

Required to restore
IESO-controlled
grid from
generating facilities
providing black-
start capability.
Circuits defining 50 kv and Positive sequence current phasor magnitude measured at terminals
Interconnection higher Positive sequence current angle magnitude measured at terminals
Reliability
Operating Limits Positive sequence voltage phasor magnitude measured at terminals
(IROL) and interties
Positive sequence voltage phasor angle measured at terminals
Frequency
Static Var Below 50 kv Positive sequence current phasor magnitude measured at terminals
Compensators Positive sequence current angle magnitude measured at terminals
(SVCs),
Synchronous Positive sequence voltage phasor magnitude measured at terminals
condensers, and Positive sequence voltage phasor angle measured at terminals
Static synchronous
compensators Frequency
(STATCOMs)

Issue 16.0 - March 5, 2025 Public Appendix 4.16–27

4 Grid Connection Requirements - Appendices

Appendix 4.17 – IESO Monitoring

Requirements: Connected Wholesale
MDP_RUL_0002_04A

Customers and Distributors

The following information, as a minimum, shall be available on a continual basis to the IESO
from all distributors connected to the IESO-controlled grid, distributors designated pursuant
to section 7.5.2 and connected wholesale customers. Needs of the state estimation process or
other reasons may result in additional requirements. The direction of all real and reactive
power flows shall be indicated measurements. A connected wholesale customer that is also a
generator shall also comply with the applicable requirements of Appendix 4.15.

Appendix 4.17–28 Public Issue 16.0 - March 5, 2025

Market Rules for the Ontario Electricity Market

TYPE
Distributor connected to
the IESO-controlled grid
or designated pursuant
to section 7.5.2
MONITORED QUANTITIES

•
Grid Connection Requirements - Appendices

Where high voltage (HV) Potential Transformers (PTs) are available:

4
Circuits: (where applicable)
• Megawatt (MW), megavars (MVARs) and direction of power flow at each
terminal connected to the IESO-controlled grid.
Transformers:
• MW, MVARS
• phase to ground voltages for each HV winding as specified by the IESO
• Where only low voltage PTs are available:
• MW, MVARs for each Low Voltage (LV) winding, and
• phase to phase voltage for each LV winding as specified by the IESO.
• Under Load Tap Changer (ULTC) tap positions.
• Off Load Tap Changer (OLTC) tap positions may be required, as directed by
the IESO
• Status of breakers or isolating switches for low voltage capacitors that are
part of the IESO-controlled grid, or that are subject to a contracted ancillary
services contract including by means or within the scope of an agreement
similar in nature to an operating agreement entered into with the connected
wholesale customer
• Status of:
• All breakers 50 kV and above.
• All line disconnect switches 50 kV and above.
• All transformer disconnect and by-pass switches 50 kV and above.
• All bus sectionalising switches 50 kV and above.
• transformer LV winding breakers and bus tie breakers for DESN type step-
down transformers connected to the IESO-controlled grid
The status of breaker isolating switches is not required.
• Remedial Action Schemes as directed by the IESO on a case by case basis.

Issue 16.0 - March 5, 2025 Public Appendix 4.17–29

4 TYPE
Grid Connection Requirements - Appendices

Connected wholesale
customers
MONITORED QUANTITIES

For:
MDP_RUL_0002_04A

• All dispatchable loads; and

Each non-dispatchable load facility that includes a non-dispatchable load rated at 20
MVA or higher or is comprised of non-dispatchable loads the ratings of which in the
aggregate equals or exceeds 20 MVA, in each case where directed by the IESO if
transmitter data is not adequate the following shall be monitored:
Where high voltage PTs are available:
Circuits: (where applicable)
• Megawatts (MW), and Megavars (MVAR) and direction of power flow at each
terminal connected to the IESO-controlled grid.
Transformers:
• Megawatts (MW), and Megavars (MVAR) and
• phase to ground voltages for each HV winding as specified by the IESO.
Where only low voltage PTs are available:
• MW, MVARs from each LV winding, and
• phase to phase voltages for each LV winding as specified by the IESO.
• Under Load Tap Changer (ULTC) tap positions.
• Off Load Tap Changer (OLTC) tap positions may be required, as directed
by the IESO
• Status of:
• All breakers 50 kV and above.
• All line disconnect switches 50 kV and above.
• All transformer disconnect and by-pass switches 50 kV and above.
• All bus sectionalising switches 50 kV and above.
• Transformer LV winding breakers and bus tie breakers for DESN type
step-down transformers connected to the IESO-controlled grid
• Breakers or isolating switches for low voltage capacitors that are part of
the IESO-controlled grid or that are subject to a contracted ancillary
services contract including by means or within the scope of an agreement
similar in nature to an operating agreement entered into with the
connected wholesale customer
The status of breaker isolating switches is not required
• Remedial Action Schemes (RAS) as directed by the IESO

Appendix 4.17–30 Public Issue 16.0 - March 5, 2025

Market Rules for the Ontario Electricity Market

Appendix 4.18 – IESO Monitoring

Requirements: Embedded Load
Grid Connection Requirements - Appendices

4
Consumers
The following information, as a minimum, shall be available on a continual basis to the IESO
from all embedded load consumers designated by the IESO pursuant to section 7.6.1. Needs
of the state estimation process or other reasons may result in additional requirements. The
direction of all real and reactive power flows shall be indicated measurements. An embedded
load consumer that is also a generator shall also comply with the applicable requirements of
Appendix 4.15.

TYPE SIZE MONITORED QUANTITIES

Dispatchable load • Megawatts (MW),
• megavars (MVAR) as designated by the IESO as
required to maintain reliable operation of the IESO-
controlled grid,
• phase to phase voltages as specified by the IESO,
and
• status of breakers or isolating switches for low
voltage capacitors that are part of the IESO-
controlled grid or that are subject to a contracted
ancillary services contract including by means or
within the scope of an agreement similar in nature
to an operating agreement entered into with the
embedded load consumer
Non-dispatchable load For a non-dispatchable Where directed by the IESO if transmitter or distributor data
load facility that is not sufficient,
includes a non-
dispatchable load rated • MW, MVAR,
at 20 MVA or higher or • phase to phase voltages as specified by the IESO;
that is comprised of and
non-dispatchable loads
the ratings of which in • status of breakers or isolating switches for low
the aggregate equals or voltage capacitors that are part of the IESO-
exceeds 20 MVA controlled grid or that are subject to a contracted
ancillary services contract including by means or
within the scope of an agreement similar in nature
to an operating agreement entered into with the
embedded load consumer

Issue 16.0 - March 5, 2025 Public Appendix 4.18–31

4 Grid Connection Requirements - Appendices

Appendix 4.19 – IESO Monitoring

Requirements: Generator Performance
MDP_RUL_0002_04A

Standards
The following performance standards, as a minimum, shall be achieved on a continual basis
by all generators referred to in section 7.3.1 of this Chapter when monitored by the IESO.
Needs of the state estimation process or other reasons may result in additional requirements.
The direction of all real and reactive power flows shall be indicated measurements.

FUNCTION Major generation Minor generation Small generation facility

facility or significant facility and
generation facility intermittent
generator or
(High Performance) transitional
scheduling
generator
designated pursuant
to section 7.3.2.3
(Medium
Performance)
Data measurements available Less than 2 seconds 1. Less than 10 Not applicable
seconds from
at the IESO communications from change in field change in field
interface monitored quantity monitored quantity or
2. If the minor
generation facility is
embedded within a
distribution system,
less than one minute
from change in field
monitored quantity
unless otherwise
designated by the
IESO to maintain the
reliability of the
IESO-controlled grid.
Equipment status change Less than 2 seconds 1. Less than 10 Not applicable
seconds from field
available at the IESO from field status status change or
communications interface change 2. If the minor
generation facility is
embedded within a
distribution system,
less than one minute
from change in
equipment status
unless otherwise
designated by the
IESO to maintain the
reliability of the
IESO-controlled grid.

Appendix 4.19–32 Public Issue 16.0 - March 5, 2025

Market Rules for the Ontario Electricity Market

FUNCTION Major generation

facility or significant
generation facility
(High Performance)
Grid Connection Requirements - Appendices

Minor generation
facility and
intermittent
generator or
transitional
Small generation facility
4
scheduling
generator
designated pursuant
to section 7.3.2.3
(Medium
Performance)
IESO scan period for data Maximum:* 4 Minimum:** 4 Not applicable
measurements seconds seconds
IESO scan period for Maximum:* 4 Minimum:** 4 Not applicable
Equipment Status seconds seconds
Data Skew Maximum: 4 Not applicable Not applicable
seconds

[Intentionally left blank –

section deleted]
[Intentionally left blank –
section deleted]

* The IESO may scan more frequently than the maximum.

** The IESO may scan less frequently than the minimum.

Issue 16.0 - March 5, 2025 Public Appendix 4.19–33

4 Grid Connection Requirements - Appendices

Appendix 4.20 – IESO Monitoring

Requirements: Transmitter Performance
MDP_RUL_0002_04A

Standards
The following performance levels, as a minimum, shall be achieved on a continual basis by
all transmitters when monitored by the IESO. Needs of the state estimation process or other
reasons may result in additional requirements. The direction of all real and reactive power
flows shall be indicated measurements.
PERFORMANCE LEVEL FACILITIES
All facilities and assets at 50 kV and above which are
monitored for system limits such as transformer or
switching stations
All transformer and switching stations with
For transmission facilities or assets designated by the interconnected ties
IESO as high performance at the time of registration,
must meet the high performance levels in Appendix An RTU which collects information at several locations
4.21 on the electricity system
Step-down transformer facilities that supply a
dispatchable load facility that is required to meet high
performance monitoring standard
All other facilities where medium performance is not
specified below
Step-down transformer facilities that supply a
dispatchable load facility that is required to meet
medium performance monitoring standard
For transmission facilities or assets designated by the Step-down transformer facilities that supply a non-
IESO as medium performance at the time of dispatchable load facility that includes a non-
registration, must meet the medium performance levels dispatchable load rated at 20 MVA or higher or that
in Appendix 4.21 comprises non-dispatchable loads the ratings of which
in the aggregate equals or exceeds 20 MVA
Facilities and assets at 50 kV and above designated
by the IESO as requiring medium performance

Appendix 4.20–34 Public Issue 16.0 - March 5, 2025

Market Rules for the Ontario Electricity Market

Appendix 4.21 – IESO Monitoring

Requirements: Transmitter Performance
Grid Connection Requirements - Appendices

4
Standards
The following performance standards, as a minimum, shall be achieved on a continual basis
by all transmitters when monitored by the IESO. Needs of the state estimation process or
other reasons may result in additional requirements. The direction of all real and reactive
power flows shall be indicated measurements.

FUNCTION Transmission facilities or assets Transmission facilities or assets

identified as high performance in identified as medium
Appendix 4.20 performance in Appendix 4.20
Data measurements available at the Less than 2 seconds from change in field Less than 10 seconds from
IESO communications interface monitored quantity change in field monitored
quantity
Equipment status change available at Less than 2 seconds from field status Less than 10 seconds from field
the IESO communications interface change status change
Data Skew Maximum: 4 seconds N/A
IESO scan period for data Maximum: 4 seconds* Minimum:** 4 seconds
measurements
IESO scan period for equipment Maximum: 4 seconds* Minimum:** 4 seconds
status

* The IESO may scan more frequently than the maximum.

** The IESO may scan less frequently than the minimum.

Issue 16.0 - March 5, 2025 Public Appendix 4.21–35

4 Grid Connection Requirements - Appendices

Appendix 4.22 – IESO Monitoring

Requirements: Distributors and Connected
MDP_RUL_0002_04A

Wholesale Customer Performance

Standards
The following performance standards, as a minimum, shall be achieved on a continual basis
by all distributors connected to the IESO-controlled grid, distributors designated pursuant to
section 7.5.2 and connected wholesale customers when monitored by the IESO. Needs of the
state estimation process or other reasons may result in additional requirements. The direction
of all real and reactive power flows shall be indicated measurements. A connected wholesale
customer that is also a generator shall also comply with the requirements of Appendix 4.19.

FUNCTION Major Dispatchable Load Facility Minor Dispatchable Load Facility and Non-
and Significant Dispatchable Dispatchable Load Facility*** that includes a non-
Load Facility dispatchable load rated at 20 MVA or higher or is
comprised of non-dispatchable loads the ratings of
(High Performance) which in the aggregate equals or exceeds 20 MVA
(Medium Performance)

Data measurements Less than 2 seconds from Less than 10 seconds from change in field
available at the IESO change in field monitored monitored quantity
communications quantity
interface
Equipment status Less than 2 seconds from field Less than 10 seconds from field status change
change available at status change
the IESO
communications
interface
Data skew Maximum:* 4 seconds Not applicable
IESO scan period for Maximum:* 4 seconds Minimum:** 4 seconds
data measurements
IESO scan period for Maximum:* 4 seconds Minimum:** 4 seconds
equipment status

* The IESO may scan more frequently than the maximum.

** The IESO may scan less frequently than the minimum.
*** Where directed by the IESO if transmitter data is not adequate.

Appendix 4.22–36 Public Issue 16.0 - March 5, 2025

Market Rules for the Ontario Electricity Market

Appendix 4.23 – IESO Monitoring

Requirements: Embedded Load
Grid Connection Requirements - Appendices

4
Consumers Performance Standards
The following performance standards, as a minimum, shall be achieved on a continual basis
by all embedded load consumers designated pursuant to section 7.6.1 when monitored by the
IESO. Needs of the state estimation process or other reasons may result in additional
requirements. The direction of all real and reactive power flows shall be indicated
measurements. An embedded load consumer that is also a generator shall also comply with
the requirements of Appendix 4.19.

FUNCTION Major Dispatchable Load Minor Dispatchable Load Facility and Non-
Facility and Significant dispatchable Load Facility*** that includes a
Dispatchable Load Facility non-dispatchable load rated at 20 MVA or
higher or is comprised of non-dispatchable
(High Performance) loads the ratings of which in the aggregate
equals or exceeds 20 MVA
(Medium Performance)
Data measurements Less than 2 seconds from 1. Less than one minute from change in field
monitored quantity; or
available at the IESO change in field monitored 2. Less than 10 seconds from change in field
communications interface quantity monitored quantity if designated by the IESO as
required to maintain reliable operation of the
IESO-controlled grid.
Equipment status change Less than 2 seconds from field 1. Less than one minute from change in field
monitored quantity; or
available at the IESO status change 2. Less than 10 seconds from field status change if
communications interface designated by the IESO as required to maintain
reliable operation of the IESO-controlled grid.
Data skew Maximum:* 4 seconds Not applicable
IESO scan period for data Maximum:* 4 seconds Minimum:** 4 seconds
measurements
IESO scan period for Maximum:* 4 seconds Minimum:** 4 seconds
equipment status

* The IESO may scan more frequently than the maximum.

** The IESO may scan less frequently than the minimum.
*** Where directed by IESO if transmitter or distributor data is not adequate.

Issue 16.0 - March 5, 2025 Public Appendix 4.23–37

4 Grid Connection Requirements - Appendices

Appendix 4.24 – IESO Monitoring

Requirements: Electricity Storage
MDP_RUL_0002_04A

Participants
The following information, as a minimum, shall be available on a continual basis to the IESO
from:

(a) any electricity storage participant (i) whose electricity storage facility is connected to the
IESO-controlled grid, or (ii) that is participating in the IESO-administered markets; and

(b) any embedded electricity storage participant (i) that is not a market participant or whose
embedded electricity storage facility is not a registered facility; (ii) whose embedded
electricity storage facility includes an electricity storage unit with an electricity storage unit
size rated at greater than 20 MVA or that comprises multiple electricity storage units, the
aggregated electricity storage unit size ratings of which exceeds 20 MVA; and (iii) that is
designated by the IESO for the purposes of section 7.3.1 of this Chapter as being required to
provide such data in order to enable the IESO to maintain the reliability of the IESO-
controlled grid.

TYPE INFORMATION REQUIREMENTS

Major electricity Monitored Quantities

storage facility
1. Active Power (MW) and Reactive Power (MX) injected or withdrawn
a) The standard requirement for active and reactive power is the provision of net MW and net MX
or gross MX. Gross MW and gross MX or net MX are also to be provided, if designated by the
IESO as required for:
(i) determination of operating security limits;
(ii) to maintain reliable operation of the IESO-controlled grid;
(iii) for compliance monitoring purposes; or
(iv) if provision of only the standard requirement values as defined above would have a negative
impact on other market participants through reduced operating security limits.
b) For electricity storage units with an electricity storage unit size greater than or equal to 100 MVA,
the standard requirement as defined in part a) for each electricity storage unit shall be provided,
and gross MW and gross MX or net MX for each electricity storage unit shall be provided if
designated by the IESO as required using the criteria listed above in part a).
c) For electricity storage units with an electricity storage unit size of less than 100 MVA:
(i) for a group of electricity storage units if those electricity storage units are similar in size and
operating characteristics, the standard requirement as defined in part a) shall be provided as
a total for these electricity storage units, and total gross MW and gross MX shall be provided
if designated by the IESO as required using the criteria listed above in part a); or

Appendix 4.23–38 Public Issue 16.0 - March 5, 2025

Market Rules for the Ontario Electricity Market

TYPE
Grid Connection Requirements - Appendices

INFORMATION REQUIREMENTS
4
(ii) if designated by the IESO as required for determination of operating security limits or to
maintain reliable operation of the IESO-controlled grid or for compliance monitoring purposes,
the standard requirement as defined in part a) for each electricity storage unit shall be
provided, and gross MW and gross MX or net MX for each electricity storage unit shall be
provided if designated by the IESO as required using the criteria listed above in part a).
d) For electricity storage facilities that have been aggregated pursuant to Chapter 7 section 2.3:
(i) the standard requirement as defined in part a) shall be provided as an aggregated total, and
an aggregated total gross MW and gross MX or net MX shall be provided if designated by the
IESO as required using the criteria listed above in part a); or
(ii) if so designated by the IESO as required for determination of operating security limits or to
maintain reliable operation of the IESO-controlled grid or for dispatch compliance monitoring
purposes, the standard requirement as defined in part a) for each electricity storage unit shall
be provided, and gross MW and gross MX or net MX for each electricity storage unit shall be
provided if designated by the IESO as required using the criteria listed above in part a).

2. State of Charge and Charge Limit

a) For each electricity storage unit or electricity storage facility, the state of charge of the applicable
electricity storage unit or electricity storage facility
b) For each electricity storage unit or electricity storage facility, the economic maximum charge limit
and the economic minimum charge limit expressed in MWh as per the applicable market
manual.

3. Base point
a) For each electricity storage unit or electricity storage facility, providing regulation, the basepoint,
if applicable, of the electricity storage unit expressed in MW, according to the applicable market
manual.

4. Dynamic Maximum and Minimum Power

a) For each electricity storage unit or electricity storage facility, the economic maximum power
mode and economic minimum power mode, expressed in MW.

5. Voltage:
a) For each electricity storage unit, unit terminal voltage, except if electricity storage units are
connected to a common low voltage bus section, then the bus section voltage is adequate for
those electricity storage units.

6. Equipment Status
a) Voltage Control status and stabilizer status (if applicable) for each electricity storage unit with an
electricity storage unit size > 100 MVA. When applicable, stabilizer status reporting is only
required if it can be switched off by electricity storage participant personnel remotely or at the
facility.
b) AGC status for each electricity storage unit providing regulation.
c) Voltage control status and stabilizer status (if applicable) for each electricity storage unit with an
electricity storage unit size < 100 MVA if the status of this equipment is designated by the IESO
as required for determination of operating security limits or to maintain reliable operation of the
IESO-controlled grid. When applicable, stabilizer status reporting is only required if it can be
switched on or off by market participant operating personnel remotely or at the facility.
d) Synchronizing Breaker status for each electricity storage unit. Where a electricity storage facility
is designed such that no low voltage synchronizing breaker is installed for each electricity
storage unit, the status of the appropriate HV breaker(s) and disconnect switch(es) normally
used to isolate the electricity storage unit must be provided. Where this results in access to the
majority of breakers on a bus, the status of the remainder of the breakers shall be provided to
complete the bus configuration.

Issue 16.0 - March 5, 2025 Public Appendix 4.23–39

4 Grid Connection Requirements - Appendices

TYPE INFORMATION REQUIREMENTS

MDP_RUL_0002_04A

e) Where a electricity storage facility is designed such that there are disconnect switches in
parallel, or directly in series, with the synchronizing breaker, the status of those switches is also
required.
f) Remedial Action Scheme status for each applicable electricity storage unit.

Significant Monitored Quantities

electricity storage
facility and minor 1. Active Power (MW) and Reactive Power (MX) injected or withdrawn:
electricity storage a) The standard requirement for active and reactive power is the provision of net MW and net MX
facility connected to or gross MX facility. Gross MW and gross MX or net MX are also to be provided, if designated
IESO-controlled by the IESO as required for:
grid (i) determination of operating security limits;
(ii) to maintain reliable operation of the IESO-controlled grid;
(iii) for compliance monitoring purposes; or
(iv) if provision of only the standard requirement values as defined above would have a negative
impact on other market participants through reduced operating security limits.
b) For electricity storage facilities that have not been aggregated pursuant to Chapter 7 section 2.3:
(i) for a group of electricity storage units if those electricity storage units are similar in size and
operating characteristics, the standard requirement as defined in part a) shall be provided as a
total for these electricity storage units, and total gross MW and gross MX or net MX shall be
provided if designated by the IESO as required using the criteria listed above in part a);
(ii) if designated by the IESO as required for determination of operating security limits or to maintain
reliable operation of the IESO-controlled grid or for compliance monitoring purposes, the
standard requirement as defined in part a) for each electricity storage unit shall be provided, and
gross MW and gross or net MX for each electricity storage unit shall be provided if designated
by the IESO as required using the criteria listed above in part a).
c) For electricity storage facilities that have been aggregated pursuant to Chapter 7 section 2.3:
(i) the standard requirement as defined in part a) shall be provided as an aggregated total, and an
aggregated total gross MW and gross MX or net MX shall be provided if designated by the IESO
as required using the criteria listed above in part a); or
(ii) if so designated by the IESO as required for determination of operating security limits or to
maintain reliable operation of the IESO-controlled grid or for dispatch compliance monitoring
purposes, the standard requirement as defined in part a) for each electricity storage unit shall be
provided, and gross MW and gross MX or net MX for each electricity storage unit shall be
provided if designated by the IESO as required using the criteria listed above in part a).

2. Voltage:
a) For electricity storage units that are VAR dispatchable, unit terminal voltage, except if the
electricity storage units are connected to a common low voltage bus section, then the bus
section voltage is adequate for those electricity storage units.

3. State of Charge and Charge Limit

a) For each electricity storage unit or electricity storage facility, the state of charge of the applicable
electricity storage unit or electricity storage facility
b) For each electricity storage unit or electricity storage facility, the economic maximum charge limit
and the economic minimum charge limit expressed in MWh as per the applicable market
manual.

4. Dynamic Maximum and Minimum Power

Appendix 4.23–40 Public Issue 16.0 - March 5, 2025

Market Rules for the Ontario Electricity Market

TYPE
Grid Connection Requirements - Appendices

INFORMATION REQUIREMENTS

a) For each electricity storage unit or electricity storage facility, the economic maximum power
mode and economic minimum power mode, expressed in MW. 5. Base point
4
a) For each electricity storage unit or electricity storage facility, providing regulation, the basepoint,
if applicable, of the storage unit expressed in MW, according to the applicable market manual.

5. Equipment Status
a) Automatic Voltage Control and stabilizer status (if applicable) for each electricity storage unit if
the status of this equipment is designated by the IESO as required for determination of
operating security limits or to maintain reliable operation of the IESO-controlled grid. When
applicable, stablizer status reporting is only required if it can be switched on or off by the market
participant operating personnel remotely or at the facility.
b) Synchronizing Breaker Status for each electricity storage unit. Where an electricity storage
facility is designed such that no low voltage synchronizing breaker is installed for each electricity
storage unit, the status of the appropriate HV breaker(s) and disconnect switch(es) normally
used to isolate the electricity storage unit must be provided. Where this results in access to the
majority of breakers on a bus, the status of the remainder of the breakers shall be provided to
complete the bus configuration.
Where an electricity storage facility is designed such that there are disconnect switches in parallel,
or directly in series, with the synchronizing breaker, the status of those switches is also required.
c) Remedial Action Scheme status for each applicable electricity storage unit.

Self-scheduling Monitored Quantities

electricity storage
facility with a name-
plate rating of less 1. Active Power (MW) and Reactive Power (MX) injected or withdrawn:
than 10 MW
a) The standard requirement for active and reactive power is the provision of net MW and net MX
or gross MX. Gross MW and gross MX or net MX are also to be provided, if designated by the
IESO as required for:
(i) determination of operating security limits;
(ii) to maintain reliable operation of the IESO-controlled grid;
(iii) for compliance monitoring purposes; or
(iv) if provision of only the standard requirement values as defined above would have a negative
impact on other market participants through reduced operating security limits.
b) For electricity storage facilities that have not been aggregated pursuant to Chapter 7 section 2.3:
(i) for a group of electricity storage units if those electricity storage units are similar in size and
operating characteristics, the standard requirement as defined in part a) shall be provided as
a total for these electricity storage units, and total gross MW and gross MX or net MX shall
be provided if designated by the IESO as required using the criteria listed above in part a);
(ii) if designated by the IESO as required for determination of operating security limits or to
maintain reliable operation of the IESO-controlled grid or for compliance monitoring
purposes, the standard requirement as defined in part a) for each electricity storage unit
shall be provided, and gross MW and gross MX or net MX for each electricity storage unit
shall be provided if designated by the IESO as required using the criteria listed above in part
a).
c) For electricity storage facilities that have been aggregated pursuant to Chapter 7 section 2.3:
(i) the standard requirement as defined in part a) shall be provided as an aggregated total, and
an aggregated total gross MW and gross MX or net MX shall be provided if designated by
the IESO as required using the criteria listed above in part a); or
(ii) if so designated by the IESO as required for determination of operating security limits or to
maintain reliable operation of the IESO-controlled grid or for dispatch compliance monitoring

Issue 16.0 - March 5, 2025 Public Appendix 4.23–41

4 Grid Connection Requirements - Appendices

TYPE INFORMATION REQUIREMENTS

MDP_RUL_0002_04A

purposes, the standard requirement as defined in part a) for each electricity storage unit
shall be provided, and gross MW and gross MX or net MX for each electricity storage unit
shall be provided if designated by the IESO as required using the criteria listed above in part
a).

2. Voltage:
a) For electricity storage units that are VAR dispatchable, unit terminal voltage, except if the
electricity storage units are connected to a common low voltage bus section, then the bus
section voltage is adequate for those electricity storage units.

3. State of Charge and Charge Limit

a) For each electricity storage unit or electricity storage facility, the state of charge of the applicable
electricity storage unit or electricity storage facility
b) For each electricity storage unit or electricity storage facility the economic maximum charge limit,
the economic minimum charge limit expressed in MWh

4. Dynamic Maximum and Minimum Power

a) For each electricity storage unit, the economic maximum power mode and economic minimum
power mode, expressed in MW.

5. Base point
a) For each electricity storage unit, providing regulation, the basepoint of the applicable electricity
storage unit expressed in MW according to the applicable market manual.

6. Equipment Status
a) Automatic Voltage Control status and Stabilizer status (if applicable) for each electricity storage
unit if the status of this equipment is designated by the IESO as required for determination of
operating security limits or to maintain reliable operation of the IESO-controlled grid. When
applicable, stablizer status reporting is only required if it can be switched on or off by market
participant operating personnel remotely or at the facility.
b) Synchronizing Breaker Status for each electricity storage unit. Where an electricity storage
facility is designed such that no low voltage synchronizing breaker is installed for each electricity
storage unit, the status of the appropriate HV breaker(s) and disconnect switch(es) normally
used to isolate the electricity storage unit must be provided. Where this results in access to the
majority of breakers on a bus, the status of the remainder of the breakers shall be provided to
complete the bus configuration.
Where an electricity storage facility is designed such that there are disconnect switches in parallel,
or directly in series, with the synchronizing breaker, the status of those switches is also required.
c) Remedial Action Scheme status for each applicable electricity storage unit.

Small electricity None

storage facility
Minor electricity Monitored Quantities
storage facility that
is embedded in a 1. Total active power (MW) output of the individual electricity storage unit or of the
distribution system aggregated resource.
and registered as a a) Unit status if the facility is comprised of a single electricity storage unit.
dispatchable
electricity storage b) Aggregated resource status if the facility is comprised of aggregated resources,
participant i.e. if at least one unit of the aggregated resource is synchronized, the aggregated
resource is synchronized or if no unit in the aggregated resource is synchronized,
the aggregated resource is not synchronized.

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Market Rules for the Ontario Electricity Market

TYPE

c)
Grid Connection Requirements - Appendices

INFORMATION REQUIREMENTS
4
Reactive Power (MX) output, if requested by the IESO for reliable operation of the
IESO-controlled grid, of individual electricity storage units or of the aggregated
resource.
d) Unit terminal voltage (kV) if requested by the IESO for reliable operation of the
IESO controlled grid

2. State of Charge and Charge Limit

a) For each electricity storage unit or electricity storage facility, the state of charge of
the applicable electricity storage unit or electricity storage facility expressed as a
percentage
b) For each electricity storage unit or electricity storage facility, the economic
maximum charge limit, the economic minimum charge limit expressed in MWh
3. Dynamic Maximum and Minimum Power
a) For each electricity storage unit or electricity storage facility, the economic
maximum power mode and economic minimum power mode, expressed in MW.
4. Base point
a) For each electricity storage unit or electricity storage facility, providing regulation,
the basepoint, if applicable, of the electricity storage unit expressed in MW
according to the applicable market manual.

Issue 16.0 - March 5, 2025 Public Appendix 4.23–43

4 Grid Connection Requirements - Appendices

Appendix 4.25 – IESO Monitoring

Requirements: Electricity Storage
MDP_RUL_0002_04A

Performance Standards
The following performance standards, as a minimum, shall be achieved on a continual basis
by all electricity storage participants referred to in section 7.3.A of this Chapter when
monitored by the IESO. Needs of the state estimation process or other reasons may result in
additional requirements. The direction of all real and reactive power flows shall be indicated
measurements.

FUNCTION Major electricity Minor electricity Small electricity storage

storage facility or storage facility and facility
significant electricity self-scheduling
storage facility electricity storage
facility (electricity
(High Performance) storage facility unit
size <10MW)
(Medium
Performance)
Data measurements available Less than 2 seconds 1. Less than 10 Not applicable
at the IESO communications from change in field seconds from
interface monitored quantity change in field
monitored quantity
or
2. If the minor
electricity storage
facility is
embedded within a
distribution
system, less than
one minute from
change in field
monitored quantity
unless otherwise
designated by the
IESO to maintain
the reliability of the
IESO-controlled
grid.

Appendix 4.23–44 Public Issue 16.0 - March 5, 2025

Market Rules for the Ontario Electricity Market

FUNCTION Major electricity

storage facility or
significant electricity
storage facility
(High Performance)
Grid Connection Requirements - Appendices

Minor electricity
storage facility and
self-scheduling
electricity storage
facility (electricity
Small electricity storage
facility
4
storage facility unit
size <10MW)
(Medium
Performance)
Equipment status change Less than 2 seconds 1. Less than 10 Not applicable
available at the IESO from field status seconds from field
communications interface change status change or
2. If the minor
electricity storage
facility is
embedded within a
distribution
system, less than
one minute from
change in
equipment status
unless otherwise
designated by the
IESO to maintain
the reliability of the
IESO-controlled
grid.
IESO scan period for data Maximum:* 4 Minimum:** 4 Not applicable
measurements seconds seconds
IESO scan period for Maximum:* 4 Minimum:** 4 Not applicable
Equipment Status seconds seconds
Data Skew Maximum: 4 Not applicable Not applicable
seconds

* The IESO may scan more frequently than the maximum.

** The IESO may scan less frequently than the minimum.

Issue 16.0 - March 5, 2025 Public Appendix 4.23–45