Electronic Voltage Protection Phase Sequence Relayzahra relay

Electronic Voltage Protection Phase Sequence Relay

Model Name: Zahra RST-25

2. Operation Instructions

The electronic phase failure relay RST 25 oers phase failure, phase shift, phase ashing, asymmetric,

phase sequence and also under and overvoltage control

3. Connection

The RST 25 can be connected as following in the installation diagram:

FIG 1: Connection of the relay before the operation.

When the relay is connected as in FIG 1, the three yellow LED’s L1, L2 and L3 light up when the power

supply A1 phase L, the A2 Neutral, and the three phases “L1”, “L2” and “L3” are properly connected.

If there is no under of overvoltage, phase failure of phase sequence, the green LED lights up, (terminals 11

and 14 are closed) and the relay is ready for operation.

FIG 2: Connection of the relay after the operation.

When the relay is connected as in FIG 2, (the power supply A1 phase L, the A2 Neutral are properly

connected) after operation, the three phases “L1”, “L2” and “L3” are properly connected, and there is no

under of overvoltage, phase failure, phase sequence, the green LED lights up (terminals 11 and 14 are

closed) and the relay is ready for self-retaining.

It is also possible to connect the power supply after an operation in FIG 2.

By both FIG’s 1 and 2, the terminal “PE” must be grounded.

4. Undervoltage

The desired Undervoltage limit can be adjusted down to -25% UN.

5. Overvoltage

The desired overvoltage limit can be adjusted up to +25% UN.

6. Asymmetry

When adjusting the overvoltage and under-voltage limit, the asymmetric limit is also adjusted7. Time Delay

The switch-o time can be adjusted by the potentiometer “Time Delay” from 0.1……5 seconds. With this

function, it is possible to adjust the time for the identication of the failure.

8. Contactor Control

If a phase fails during operation at load or one of the contacts of the contactor or circuit breaker is

defected, (contact bounce or scorched contacts), RST 25 recognizes the failure, and also the feedback

voltage, and switches o depending on the setting of “Time Delay”

The RST 25 controls the phase shift. If there is a phase failure during operation the angle from the

feedback voltage is 30℃ and the RST 25 recognizes this failure.