Voltage Control; Application - ABB RER670 Applications Manual

Section 12
Control
12.5
12.5.1
288
• QB9_OP = 1
• QB9_CL = 0
• QC9_OP = 1
• QC9_CL = 0
If, in this case, line voltage supervision is added, then rather than setting QB9 to
open state, specify the state of the voltage supervision:
• QB9_OP = VOLT_OFF
• QB9_CL = VOLT_ON
If there is no voltage supervision, then set the corresponding inputs as follows:
• VOLT_OFF = 1
• VOLT_ON = 0

Voltage control

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 on-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 on-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 at 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 can be made in three
alternative ways:
1MRK 506 375-UEN A
SEMOD158732-1 v2
SEMOD159067-1 v2
SEMOD159053-5 v5
Railway application RER670 2.2 IEC
Application manual