Frequency Protection Relay



DIN rail mounting protection relays for use in single and three phase systems. Available in 55mm x 112mm or 100 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-F1U Single or 3 phase under frequency
M200-F1O Single or 3 phase over frequency
M200-F1C Single or 3 phase combined frequency

Typical Applications

The M200 series frequency protection relays are designed to monitor the frequency of a system and if the frequency deviates outside the customer adjustable preset limits, the relay will operate. Typically used in protecting generators against under or over speed, this is achieved as speed is proportional to frequency.

Other uses such as monitoring mains power supplies, computer supplies etc. The user is provided with adjustment of both the trip point of frequency being monitored and the differential. As is common with all the M200 relays, on over units the relay energises when the input signal exceeds the trip point. A red LED indicates the state of the relay, whilst a green LED indicates the condition of the power supply. The frequency relays monitor their own power supply so no auxiliary power is required.

Technical Specification

Rated value Un 57.8<500V ±25%
Rated frequency 50/60/400Hz
Burden < 2.5VA
Overload 1.5 x Un continuous 2 x Un for 3 seconds
Range 50Hz nominal Adjustable 40 to 60Hz
Range 60Hz nominal Adjustable 50 to 70Hz
Range 400Hz Adjustable 360 to 440Hz
Differential 50 & 60Hz Adjustable 0.3 to 3Hz
Differential 400Hz Adjustable 3 to 30Hz
Repeatability Better than 0.5% of full span
Operating Time Typically 200ms
AUXILIARY All units self powered
Single units Approx 0.4kg. 55mm case
Combined Units Approx 0.6kg. 100mm case


1 On all of the above units an internally set time delay is available for any value between 1 & 10 seconds. To order use the above codes adding a D at the end of the code. e.g M200-F1U / D7 seconds (state the fixed delay period).
2 AC auxiliary in range 57.7 to 480 volts
3 To prevent nuisance tripping when there is a slight variation in the frequency the following option is available. The external differential is replaced with an external time delay. On these units the time delay is adjustable from 200mS to 10 second, and the differential is fixed at 1%.
M200-F1X: Single or 3 phase under frequency
M200-F1Y: Single or 3 phase over frequency
M200-F1W: Single or 3 phase combined frequency
4 Calibration at temperature other than 23ºC

Connection Diagrams