Protection and Coordination
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Protection & Coordination
• Agenda
– Objectives
– Study Procedure & Required Data
– Overcurrent Protection
– Overcurrent Coordination
– STAR Overview & ETAP 14 Enhancements
• Features and Capabilities
• Protective Device & Library
• STAR Short-circuit
• PD Sequence of Operation
• Normalized TCC curves
• TCC Print and Settings Report
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Protection & Coordination
• Objectives
– Human Safety
• Prevent injury and fatality
– Protection of Equipment
• Permit normal operation
• Isolate the equipment in case of abnormal conditions
– Selectivity / Grading / Discrimination
• Minimal isolation of network with abnormal conditions
• Permit normal operation for rest of electrical network
– Reliability and Cost
• Maximum achievable reliability for protection and coordination at
minimal cost
©2015 ETAP PROPRIETARY & CONFIDENTIAL
References
• IEEE Std. 242-2001, IEEE Recommended Practice for Protection
and Coordination of Industrial and Commercial Power Systems
(IEEE Buff Book)
• IEEE Std. 141-1993, IEEE Recommended Practice for Electric
Power Distribution for Industrial Plants (IEEE Red Book)
• IEEE Std. 399-1997, IEEE Recommended Practice for Industrial
and Commercial Power Systems Analysis (IEEE Brown Book)
• Other technical references
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Study Procedure
• Prepare an accurate one-line diagram (relay
diagrams)
• Obtain the available system current spectrum
(operating load, overloads, fault kA)
• Determine the equipment protection criteria
• Select the appropriate protective devices / settings
• Plot the fixed points (operating/damage curves, FLA,
ampacity, etc.)
• Obtain / plot the device characteristics curves
• Analyze the results
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Required Data
• One-line diagrams (Relay diagrams)
• Power Grid Fault Current Data and Protective Device Settings
• Generator Data
• Transformer Data
• Motor Data
• Load Data
• Fault Currents
• Cable / Conductor Data
• Bus / Switchgear Data
• Instrument Transformer Data (CT, VT)
• Protective Device (PD) Data
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Overcurrent Protection
• Major Equipments (apparatus)
– Induction Motor
– Synchronous Motor
– Cable
– Transformer
– Generator
– Bus
– Transmission/Distribution Line
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Excessive Currents
• Excessive currents in abnormal conditions
– Overload current
• (100-160% Full Load Amps)
– Short-time overload current
• (300-1000% Full Load Amps)
– Short-circuit current
• (300-1200% Full Load Amps)
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Capability / Damage Curves
2
It I2t I2t
t
I22t
Motor
Xfmr Cable
Gen
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Protective Devices
Overcurrent Characteristics Time-Current-Characteristics (TCC)
• Inverse Time Over Current
• Simple, cheap, and large
application in LV, and MV
• Relays (OC & OL)
• No tolerance band
• TOC, IOC
• Single / Multiple Function
• LV Breakers
• Represent tolerance band
• PCB/ACB, ICCB, MCCB, MCB
• Fuses
• Overload Heater
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Overcurrent Protection
Protection Concept Motor Protection Example
• Protective Device TCC
– To the left and below of
equipment damage curve
– To the right and above of
equipment operating curve
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Selective Coordination
• Overcurrent Selectivity Rules
– Downstream device curve is located to the left and below
of upstream device curve for range of applicable currents
– Sufficient time margin for operation of downstream before
upstream
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Margins for Selectivity*
• Relay - Relay
– 0.12 to 0.22 seconds + downstream breaker opening time
• Relay – Fuse / Low Voltage Circuit Breaker
– 0.12 to 0.22 seconds
• Fuse / Low Voltage Circuit Breaker - Relay
– 0.12 seconds + downstream breaker opening time
• Fuse / Low Voltage Circuit Breaker - Fuse / Low Voltage Circuit Breaker
– Clear space between curves**
* Calibrated protective devices
* *Possible adjustment for upstream fuse preloading and safety factors
©2015 ETAP PROPRIETARY & CONFIDENTIAL
ETAP Star Overview
• Star Mode
– Star Mode and Star View difference
– Creation of TCC and Star View
– Addition of devices to existing TCC
– Graphical and Editor adjustments
– Star View Toolbars and Plot Options
©2015 ETAP PROPRIETARY & CONFIDENTIAL
ETAP Star Overview
• Supported Protective Devices and Functions
– Overload - CT based & Inline (49)
– Phase, neutral, ground, and negative sequence overcurrent
(51/50)
– Voltage control and restraint overcurrent (51VC/51VR)
– Directional overcurrent (67)
– High impedance & percentage differential (87)
– Electronic & hydraulic reclosers (79)
– Relay interlock with HVCB, switch and contactor
– CT Ratio and multiple connections
– Under / Over Voltage (27/59)
*Reverse power (32) and under/over Frequency (81) are supported in
Transient Stability
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Protective Devices
• Relays
– Microprocessor/electronic
• More expensive, faster, multiple functionality
– Electromechanical
• Simple, cheap, slower, limited functionality
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Relay ANSI Device Numbers
• 21 – Distance • P – Phase
• 27 – Under Voltage
• N – Neutral
• 32 – Directional Power
• G – Ground
• 49 – Thermal Overload
• SG – Sensitive Ground
• 50 – Instantaneous Over Current
• 51 – AC Inverse Over Current • V – Voltage
• 52 – AC Circuit Breaker • VC – Voltage Control
• 59 – Overvoltage • VR – Voltage Restrained
• 67 – AC Directional Over Current
• 79 – AC Recloser
• 81 – Frequency
• 87 – Differential
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Relay Characteristics
Relay TOC Characteristics Relay TOC Curves
• Curve Shape Adaptation
• Equipment Protection
• Selectivity
• Time Margin at higher fault
currents
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Fuse (Power Fuse)
• Non Adjustable Device (unless electronic)
• Continuous and Interrupting Rating
• Voltage Levels (Max kV)
• Interrupting Rating (sym, asym)
• Characteristic Curves
– Min. Melting
– Total Clearing
• Application (rating type: R, E, X, …)
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Fuse Types
• Expulsion Fuse (Non-CLF)
• Current Limiting Fuse (CLF)
• Electronic Fuse (S&C Fault Fiter)
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Current Limiting Fuse (CLF)
• Limits the peak current of short-circuit
• Reduces magnetic stresses (mechanical damage)
• Reduces thermal energy
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Current Limiting Action
Ip
Current (peak amps)
ta = tc – tm
Ip’
ta = Arcing Time
tm = Melting Time
tc = Clearing Time
tm ta Time (cycles) Ip = Peak Current
tc
Ip’ = Peak Let-thru Current
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Fuse
Generally:
• CLF is a better short-circuit protection
• Non-CLF (expulsion fuse) is a better Overload protection
• Electronic fuses are typically easier to coordinate due to the
electronic control adjustments
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Motor Protection
• Motor Starting Curve
• Thermal Protection
• Locked Rotor Protection
• Fault Protection
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Inrush Current
Starting Current of a 4000Hp, 12 kV, 1800 rpm Motor
First half cycle current showing
current offset.
Beginning of run up current
showing load torque pulsations.
Motor pull in current showing motor
reaching synchronous speed
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Motor Protection
LV Motor Protection MV Motor Protection
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Motor Protection
• Standards & References
– IEEE Std 620-1996 IEEE Guide for the Presentation of
Thermal Limit Curves for Squirrel Cage Induction
Machines.
– IEEE Std 1255-2000 IEEE Guide for Evaluation of Torque
Pulsations During Starting of Synchronous Motors
– ANSI/ IEEE C37.96-2000 Guide for AC Motor Protection
– NEMA MG-1 Motors and Generators
– The Art of Protective Relaying – General Electric
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Overload Relay / Heater
• Motor overload protection is provided by a device that models
the temperature rise of the winding
• When the temperature rise reaches a point that will damage
the motor, the motor is de-energized
• Overload relays are either bimetallic, melting alloy or
electronic
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Overload Relay / Heater
• When the temperature at the combination motor starter is more than ±10
°C (±18 °F) different than the temperature at the motor, ambient
temperature correction of the motor current is required.
• An adjustment is required because the output that a motor can safely
deliver varies with temperature.
• The motor can deliver its full rated horsepower at an ambient temperature
specified by the motor manufacturers, normally + 40 °C. At high
temperatures (higher than + 40 °C) less than 100% of the normal rated
current can be drawn from the motor without shortening the insulation
life.
• At lower temperatures (less than + 40 °C) more than 100% of the normal
rated current could be drawn from the motor without shortening the
insulation life.
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Motor Protection - Overload Pickup
(NEC Art 430.32 – Continuous-Duty Motors)
• Thermal O/L (Device 49) Pickup
– Motors with marked Service Factor ≥ 1.15
• Pickup = 125% of FLA
– Motors with temp. rise not over 40°C
• Pickup = 125% of FLA
– All other motors
• 115% of FLA
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Fault Protection
(NEC Art / Table 430-52)
• Non-Time Delay Fuses
– 300% of FLA
• Dual Element (Time-Delay Fuses)
– 175% of FLA
• Instantaneous Trip Breaker
– 800% - 1300% of FLA*
• Inverse Time Breakers
– 250% of FLA
*can be set up to 1700% for Design B (energy efficient) Motor
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Low Voltage Motor Protection
• Usually pre-engineered (selected from Catalogs)
• Typically, motors larger than 2 Hp are protected by
combination starters
• Overload / Short-circuit protection
©2015 ETAP PROPRIETARY & CONFIDENTIAL
(49)
I2T
O/L
tLR MCP
(51) 200 HP
ts
Starting Curve
MCP (50)
LRAs LRAasym
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Transformer Protection
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Transformer Protection
• Standards & References
– National Electric Code 2011 Edition
– IEEE Std 242-1986; IEEE Recommended Practice for Protection and
Coordination of Industrial and Commercial Power Systems
– C37.91-2000; IEEE Guide for Protective Relay Applications to Power
Transformers
– C57.12.59; IEEE Guide for Dry-Type Transformer Through-Fault
Current Duration.
– C57.109-1985; IEEE Guide for Liquid-Immersed Transformer Through-
Fault-Current Duration
– APPLIED PROCTIVE RELAYING; J.L. Blackburn; Westinghouse Electric
Corp; 1976
– PROTECTIVE RELAYING, PRINCIPLES AND APPLICATIONS; J.L.
Blackburn; Marcel Dekker, Inc; 1987
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Transformer Category IV
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Transformer
FLA
200
Thermal
t I2t = 1250
(D-D LL) 0.87
(sec)
Infrequent Fault
(D-R LG) 0.58
Frequent Fault
2
Mechanical
K=(1/Z)2t
Inrush
2.5 Isc 25 I (pu)
©2015 ETAP PROPRIETARY & CONFIDENTIAL
ETAP Star Auto-Evaluation
• Automated and intelligent detection of protection zones
• Overcurrent Protection and Coordination Evaluation
• Customized evaluation criteria based on Rule Book
• Evaluation and Fault Current Type selection in Study Case
• Tabular and graphical display of evaluation results
• Graphical snapshot and evaluation report
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Evaluation Rule Book
• Protection Rules
– Default rules based on industry practice
– Adjustable evaluation criteria based on
standards or user defined
– Support of NEC overload protection such as:
• NEC 240.101 for HV cable protection
• NEC 430.32 for motor protection
• NEC 450.3 for transformer protection
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Star Auto Study Case
• Selection of rules
• Evaluation
– Protection
– Coordination
– Protection & Coordination
• Fault Type
– Phase
– Ground (Coordination)
– Phase and Ground
• Evaluation Messages
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Results Viewer
• Tabular and graphical evaluation results
• Max through fault current
• Colorful status indication
• Extensive messages
• On the spot editing capability
• Evaluation update after modification
– Dynamic
– Static
• Rule Book View
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Results Viewer
• Graphical evaluation (Temp Star View)
– Dynamic update of view based on through fault
– Correlation between selected elements on graphical and
tabular view
– Graphical adjustment of settings
– Graphical tools
– Screen capture
©2015 ETAP PROPRIETARY & CONFIDENTIAL
Evaluation Report
• Excel
– Study assumptions
– Separate sheet for each protection zone
– Coordination sheet
– Extensive messages
– Option to have passed messages
©2015 ETAP PROPRIETARY & CONFIDENTIAL
