• Emco Electronics

Voltage Regulating Relay, Type Ee-303

Emco Electronics offers a microcontroller based automatic Voltage Regulating Relay, type EE-303. This is a new generation relay used for regulating the secondary voltage of power transformers with a motor driven on load tap changer (OLTC). A single control pulse to the motor causes a change in voltage by one step. When step by step function is inactive, the motor drive is controlled by a continuous control pulse. A 'raise' or `lower' control signal is generated by the voltage regulator when the measured voltage deviates from preset conditions. The parameters are programmable through a front panel key and are stored in non-volatile memory. Time delay setting (for deviation from deadband to the first control pulse) can be set in linear or integral mode, (i.e., inversely proportional to the deviation). The time delay between consecutive control pulses is also programmable. Relays with potential free contacts are provided for signalling 'undervoltage', 'overvoltage' and `control fail' conditions. The undervoltage, overvoltage and control fail conditions result in the blocking of the tap changer. The regulated voltage can be displayed in volts and kilovolts. LED annunciators are provided for presignal conditions and relay operations. The auto/manual selection allows the relay to operate, in the auto mode or in the manual mode. In the manual mode, the "raise" and "lower" pulses can be given through the front panel keys. The built-in TPI indicates the tap position up to a maximum of 35 taps with blocking at minimum/maximum tap. The maximum tap number is programmable. The 'test' mode allows checking of the operation of the AVR while mounted on the panel. The minimum/maximum PT voltage is stored and can be displayed when required. An indication for the tap change in progress is provided and sensed through potential free contacts. AVR disable facility is provided for remotely disabling the AVR during SCADA operation. The following features can be given optionally: a pair of NC contacts in case of failure of auxiliary supply, 4-20 mA TPI output for SCADA, and 433 V display for PT instead of 110 V.