Voltage Control; Identification; Application - ABB Relion 650 Series Applications Manual

Section 12
Control
12.2

Voltage control

12.2.1

Identification

Function description
Automatic voltage control for tap
changer
Tap changer control and supervision,
6 binary inputs
12.2.2

Application

When the load in a power network is increased the voltage will decrease and vice versa. To
maintain the network voltage at a constant level, power transformers are usually equipped
with an load tap changer. This alters the power transformer ratio in a number of predefined
steps and in that way changes the voltage. Each step usually represents a change in voltage of
approximately 0.5-1.7%.
The voltage control function is intended for control of power transformers with a motor driven
load tap changer. The function is designed to regulate the voltage at the secondary side of the
power transformer. The control method is based on a step-by-step principle which means that
a control pulse, one at a time, will be issued to the tap changer mechanism to move it one
position up or down. The length of the control pulse can be set within a wide range to
accommodate different types of tap changer mechanisms. The pulse is generated whenever
the measured voltage, for a given time, deviates from the set reference value by more than the
preset deadband (degree of insensitivity).
The voltage can be controlled at the point of voltage measurement, as well as a load point
located out in the network. In the latter case, the load point voltage is calculated based on the
measured load current and the known impedance from the voltage measuring point to the
load point.
The automatic voltage control can be either for a single transformer, or for parallel
transformers. Parallel control of power transformers with an IED can be made in three
alternative ways:
• With the master-follower method
• With the reverse reactance method
• With the circulating current method
Of these alternatives, the first and the last require communication between the function
control blocks of the different transformers, whereas the middle alternative does not require
any communication.
The voltage control includes many extra features such as possibility to avoid simultaneous
tapping of parallel transformers, extensive tap changer monitoring including contact wear and
hunting detection, monitoring of the power flow in the transformer so that for example, the
voltage control can be blocked if the power reverses and so on.
174
IEC 61850
identification
TR8ATCC
TCMYLTC
© Copyright 2011 ABB Power Grids. All rights reserved
IEC 60617 ANSI/IEEE C37.2
identification device number
90
U
IEC10000166 V1 EN-US
84
IEC10000167 V1 EN-US
Transformer protection RET650
1MRK 504 124-UEN B
GUID-750C3448-BA6E-4A17-A519-7E160E20FCF2 v2
SEMOD159053-5 v4
Application manual