Synchronysing Check Protection Relay

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DIN rail mounting protection relays for use in single and three phase systems. Available in 112mm x 112mm DIN rail cases


For over protection, under protection and combined under & over protection available in AC current AC voltage & frequency versions. Millivolt trip, DC voltage trip, Reverse Power, Phase sequence & Phase balance relays also available in our extensive range of protection relays..

Selection Guide

M200-PLL 1 generator 1 bus or 2 generators
M200-PLD 1 generator 1 bus with dead bus facility
Both units can be used on single or 3 phase systems.

Typical Applications

The M200-PLL & PLD are synchronised check relays, also known as paralleling relays. They are used to ensure that two AC supplies are synchronised, frequency, phase angle and voltage have to be within preset limits. The M200-PLL can monitor either main busbar and incoming generator, or two generators. The PLL has customer adjustment of the vifferential voltage of between 10 to 30%. This voltage corresponds to 6 to 20 electrical degrees. The unit compares the input voltage and phase relationship of the busbar as to that of the generator, when the signal is within preset limits, the relay energises. The M200-PLD operates as the M200-PLL but has the additional feature of the dead bus facility. This enables the relay to energise with a generator supply only, which is a common requirement where mains failure occurs.

Technical Specification

Rated value Un: 57.8 < 500V ±25%
Frequency: 50 / 60 / 400Hz
Burden: < 4VA terminals marked GEN<2VA terminals marked BUS
Overload: 1.5 x continuous 10 x Un for 3 seconds
Range: Adjustable 10% to 30% of nominal system voltage (6-20 electrical degrees)
Repeatability: Better than 0.5% of span
Differential: Fixed at 5%
Operating time: Typically 500mS
Both units are self powered
WEIGHT&CASE Approx 0.6kg. 100mm case

Ordering Information

Product Code System Voltage Frequency Options
M200-PLD 400V 50Hz Cal at 35ºC

Connection Diagrams