Compact relay

Single function protection relays (SFPRs) are used for time-graded current (over current or short circuit), voltage (over voltage, under voltage, voltage unbalance) and frequency protection applications. Single function or compact relays are used in low-voltage applications. They are DIN rail-mountable and are easy to install, operate and commission. The wide-range power supply for AC and DC make these relays universal. Compact relays can be single or three phase relays.

Single function protection relays use MCU with an internal ADC for measuring the electrical parameter. A seven segments LED or character LCD is provided to display measured parameters. LEDs are provided for quick indication of the load status and other system functionalities. One or two relay outputs are provided for disconnecting the load during fault conditions. The parameter settings are configured using keys, rotary switches or potentiometers provided on the front panel. An RS-485 interface with MODBUS protocol is provided for networking.

Design requirements

Modern compact relay designs can help:

• Optimize the cost, size and performance of the MCU with integrated AFE and LED drive for capturing and processing of analog input signals and implementing protection algorithm.
• Power supply designs can help improve efficiency for wide input AC and DC voltages.
• Relay drivers and seven-segment LED drivers can be used depending on the drive requirements.