ABB RELION REX640 Technical Manual page 1116

Protection and control

Hide thumbs Also See for RELION REX640:

Table of Contents

Protection functions

Blocking mode which selects the blocking mode. The BLOCK input can be controlled

by a binary input, a horizontal communication input or an internal signal of

the protection relay's program. The influence of the BLOCK signal activation is

preselected with the global setting

mode, the operation timer is frozen to the prevailing value. In the "Block all" mode,

the whole function is blocked and the timers are reset. In the "Block OPERATE

output" mode, COLPTOC is executed normally but the OPR_OVLOD and OPR_UN_I

outputs are not allowed to activate.

The application area for three-phase overload protection function of shunt

capacitor bank is the protection of power capacitor banks intended for reactive

power compensation and filtering of the harmonics. Shunt capacitor banks provide

a low-impedance path to harmonic currents and hence attract harmonic currents

flowing in the system. Increased harmonic currents result in excessive voltage stress

across the capacitor bank. According to the standards, a high-voltage capacitor

shall be able to withstand 10% overload. Loading beyond that can cause damage

to the capacitor bank and in turn to the system. Hence, COLPTOC is specially

designed for the protection against overloads produced by harmonic currents and

overvoltage.

Undercurrent protection is used to disconnect the capacitor bank from the rest

of the power system when the voltage at the capacitor bank terminals is too

low for too long a period of time. To avoid an undercurrent trip operation when

the capacitor bank is disconnected from the power system, the undercurrent

functionality is blocked by using the capacitor bank circuit breaker status signal.

Furthermore, the reclosing inhibition feature provides protection against the

reconnection of a charged capacitor to a live network. Whenever the capacitor

bank circuit breaker is opened, the reclosing is inhibited for the duration of

the discharge time of the capacitor. The reclosing inhibition functionality can be

disabled manually or automatically. In the manual mode, the inhibition reclosing

has to be manually reset and in automatic mode, the reclosing inhibitionl resets

automatically after the set time.

Blocking mode setting has three blocking methods. In the "Freeze timers"

The BLOCK input does not block the BLK_CLOSE signal.

Blocking mode .

1MRS759142 F

Technical Manual