Theory, Construction and Application

Voltage Regulator Training Schools

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Regulator Theory – Purpose
• What is Voltage Regulation?

• Voltage Regulation – Providing a consistent

sine wave with a nearly constant magnitude to
the load.

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Regulator Theory – Purpose
• Why is voltage regulation needed?
• Power quality criteria requires a constant voltage
despite variations in load current
• Voltage drops due to line losses
• Load current variations are due to:
• New loads
• Load profiles – Daily and Seasonal
LOAD VS TIME OF DAY

System
Load

12am 6am 12pm 6pm

TIME OF DAY

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Regulator Theory – Purpose
Properly designed distribution feeder

OLTC
L1 L2 L3

Maximum Acceptable Voltage Level

+5%
Light Load
Nominal
Heavy Load
Voltage
– 5%
Minimum Acceptable Voltage Level

OLTC = On-Load tap changing power transformer

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Regulator Theory – Purpose
Over Time – An increase of load density and feeder
length results in an unacceptable voltage drop.
Also, voltage can drop off due to line losses.

OLTC
L1 L4 L2 L5 L3 L6 L7

Maximum Acceptable Voltage Level

+5%
Light Load Nominal
Voltage
Heavy Load
–5%
Minimum Acceptable Voltage Level

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Regulator Theory – Purpose
Voltage Regulators: Solve voltage drop problem

R1
OLTC
L1 L4 L2 L5 L3 L6 L7

+5%

Nominal
Voltage

--5%

Applied at Substation and midpoint of Feeder.

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Regulator Theory

Voltage Regulator
Construction

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Regulator Theory – Construction
• Three basic part of a voltage regulator
• Autotransformer - A transformer in which part of
one winding is common to both the primary and
secondary windings
• Load Tap Changer - A switch designed to work
under load to change the configuration of a
transformer coil
• Voltage Regulator Control - A Control which senses
the system and automatically commands the tap
changer

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Regulator Theory – Construction

Conventional Two-winding Transformer

+ +

Vprimary = 1000V Vsecondary = 100V

-
-

Windings Ratio 10:1

Output Ratio 10:1

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Regulator Theory – Construction
Step-up Autotransformer
(+ to –) = Additive Property

+ +

Vprimary = 1000V Vsecondary = 1100V

-
-

Windings Ratio 10:1

Output Ratio 10:11

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Regulator Theory – Construction
Step-down Autotransformer
(+ to +) = Subtractive Property

+ +

Vprimary = 1000V
-
-
Vsecondary = 900V

Windings Ratio 10:1

Output Ratio 10:9

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Regulator Theory – Construction
Step Voltage Regulator

+ Stationary Contacts

1 N
+

2
3
Movable

4
Contacts
5
6
7

_
8

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 Regulator Theory – Construction
Step Voltage Regulator with Reversing Switch
Shown in Step
Down or Bucking
+ Position

1 N
+

2
3
4
5
6
7

_
8

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 Regulator Theory – Construction
Step Voltage Regulator with Reversing Switch
Question:

+
If there are 8 stationary

1 N
+ contacts, why do we call
it a 32 step regulator?

2
Answer:

3
4
8 stationary contacts
5
6 + 8 intermediate
positions = 16 steps.
7

_
Add the reversing switch
8

_
and you get 32!

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Regulator Theory – Construction
• Bridging Reactor
• Maintains continuity
during tap change
• Provides impedance
to limit current
interrupted during
tap change

Stationary
Contacts
Moveable
Bridging Contacts
Reactor

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Regulator Construction – Features

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Regulator Construction – Features
Arresters
Series Shunt

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 Regulator Construction – Features
Position Indicators
• Current Position Indicator
• Corrosion Resistant
• 20% Larger Viewing Area
• Pad-Lockable
• Lighter Weight
• Slim Profile

• Legacy Position Indicator

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Regulator Construction – Features
• Control cable
• Disconnect plug at both ends
• Easy maintenance
• Easy replacement
• No conduit
• No wiring diagrams

• CT Protection Circuit
• CT automatically shorted
when control cable is
removed
• Quicker and safer removal
of the control box and
cable for field retrofits
• Maintenance free
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 Regulator Construction – Features
Junction Box & Block Current Design Legacy Design

Inside Tank
(Under cover)
• Plug-in junction block wiring harness
• New block is completely retrofittable with existing regulators
• Prevents possibility of mis-wiring
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 Regulator Construction – Features
• Current Transformer (CT)
• Purpose – Metering and Current Flow
• Mounting
• Secure mounting around Load bushing

Current
Design

Legacy
Design

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 Regulator Construction – Features
Inspection Hand Hole
• Six-inch Diameter cover hole
• Vacuum Processing
• User access
• Inspection
• Changing CT connections

• Vacuum Oil Filling

• Moisture and air removed
Legacy Design
• Oil filled and soaked 8-24 hours
• 2mm Mercury (750 torr)

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 Regulator Construction – Features
Quik Drive Tap Changers
• Longer Life
• 20% fewer parts than traditional spring loaded devices – less maintenance, longer life, and lower life
cycle costs
• The Geneva Gear drive ensures accurate steps without the need for special calibrated springs
resulting in greater tap changing accuracy, extended contact life and less maintenance
• Improved Power Quality
• Taps all 33 positions in less than 10 seconds – 5 to 10 times faster than traditional spring drives
• The speed result in better power quality and quicker recovery from large voltage excursions, which
protects customer equipment
• Lower Operational Costs
• Installation and maintenance time is reduced, which can save time and money

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Regulator Construction – Product Scope
• Voltage regulator product offering:
• Regulation of +/- 10% in 32 - 5/8% steps
• 55/65 °C Average Winding Rise (12% more capacity)
• 25 to > 2500+ Amperes
• 50 Hz - 6600 V to 33000 V (95-200 BIL)
• 60 Hz - 2400 V to 34500 V (60-200 BIL)
• Mineral Oil or FR3 Immersed
• Fan Cooling option (33% more capacity)

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 Regulator Construction – Product Scope
• Padmount Voltage Regulators
• Aesthetically pleasing • Underground solution
• Reduced costs • Deadfront connector system
• No Overhead lines or Substation Fences • Safety
• Less overall land required • Reliability
• Easier to obtain right of way • Great green solution with FR3
• Innovative

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Regulator Construction – Product Scope
Padmount Voltage Regulators

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Regulator Construction – Product Scope
Three-in-one Padmount Voltage Regulators

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 Regulator Application - Connections
Two single-phase regulators on a 3-phase, 3-wire circuit
Bypass Switch
Phase A
Phase B
Phase C

Disconnect
Switch

L L

S SL S SL
B

60
o System
Voltage

VCB (1.0 pu) VCA

VAB (1.0 pu)
V’CB (1.1 pu) V’AB (1.1 pu)

V’CA (1.10 pu)

• 3-wire
Open Delta
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 Regulator Application - Connections
3 single-phase regulators on a 3-phase, 3-wire circuit.
Bypass Switch
Phase A
Phase B
Phase C

Disconnect
Switches

L L L

SL SL SL
S S S

A’

A
• 3-wire
V’BA (1.15 pu)
VBA
Closed Delta
V’AC (1.15 pu) (1.00 pu)
C B
C’
B’
V’CB (1.15 pu)
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© 2013 Eaton. All rights reserved.
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