A relay is an electrically operated switch. It consists of a set of input terminals for a single or multiple control signals, and a set of operating contact terminals.
Electronic Voltage Protection Phase Sequence Relay Model Name: Zahra RST-25 2. Operation Instructions The electronic phase failure relay RST 25 offers phase failure, phase shift, phase flashing, 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 adjusted. 7. Time Delay The switch-off 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 identification 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 off 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.
1 x Electronic Voltage Protection Phase Sequence Relay(zahra relay)