ABB RET670 - Application

Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Automatic voltage control for tap
changer, single control
TR1ATCC
U
IEC10000165 V1 EN
90
Automatic voltage control for tap
changer, parallel control
TR8ATCC
U
IEC10000166 V1 EN
90
Tap changer control and supervision, 6
binary inputs
TCMYLTC - 84
Tap changer control and supervision,
32 binary inputs
TCLYLTC - 84
3.12.4.1 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
Section 3 1MRK504116-UUS C
IED application
652
Application manual