KSQ331 Sector Check Synchronizing Relay

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Sector Check Synchronizing Relay
KSQ331x2 Brochure




  • Low differential check synchronizing, sector principle
  • Bi-directional synchronizing
  • Manual and semi-automatic synchronizer
  • Integral voltage differential protection
  • “Easy view” status presentation
  • System status output
The digitally controlled KSQ331x2 provides both visual presentation of relative speed and phase angle relationship, and output signal necessary to permit check synchronizing between two systems.
KSQ331E2 is the standard and it takes the auxiliary voltage from the monitored voltage on terminal 3 & 4.
KSQ331G2 have separate auxiliary supply on terminal 19 & 20.
The synchronizing relay will close when the incomer (generator, busbar, etc.) voltage and phase angle have been within the limits during the set retention time.
A green lamp (CB close) indicates the close command to the breaker.
There is lamp indication for reference source present (BUS PWR) and incomer status (GEN PWR).
A green lamp (VOLT OK) is lit when the incomer voltage is within the set limits.
KSQ331x2 can be used both for single and three phase systems. Any two phases (or phase-neutral) can be used for synchronizing as long as it is the same two phases on both side of the breaker.
The unit is meant for manual and semi-automatic synchronizing only. There is no compensation for the breaker closing time.
For automatic synchronizing the KSQ104x2 “SPOT ON” principle should be used to obtain compensation for breaker closing delay.
User settable limits and retention time on the rear.
System status:
KSQ331x2 is fitted with a system status relay. As standard the unit is powered from generator side (terminal 3 & 4), when power is ok and unit is working correctly the relay activates. It will release on alarm or when unit is not powered. Separate auxiliary supply is needed for continuously system status.
Normal operation                   : Closed contact
Alarm condition/un-powered  : Open contact
System “S” the sector synchronizing principle
The KSQ331x2 is a low differential bi-directional check synchronizing relay.
The synchronizing relay closes when the incomer (generator, busbar, etc.) frequency is close enough (diff 0,01 – 0,5Hz) to stay within the phase angle sector (S) for the set retention period (t).
Sector synchronization is the classic alternative for applications which allow synchronization accuracy and duration of synchronization process to be interrelated. There is no compensation for the breaker closing time.
Approximate synchronization accuracy relative to 12 o’clock position (Df) can be calculated by the following formula:
Df = (S : 360) / t (secs)
Example: Set phase angle (S) to 10 degrees and retention time (t) to 500mS to obtain an accuracy of Df:
(10/360) / 0,5 =  0,055Hz
If the phase angle limit is set too low and retention time too high for very low differential synchronizing, it can be difficult to achieve synchronization. If there is a continuously fluctuating load between the two systems (for example to synchronize against a shaft generator when a vessel is in rough weather), the KCQ104x2 “SPOT-ON” principle is more suitable.

Additional information

Weight 2 lbs
Dimensions 9 × 9 × 9 in

KSQ331E2 Sector Check Synchronizing Relay w/o Aux Supply, KSQ331G2 Sector Check Synchronizing Relay w Aux Supply

Monitored Voltage

100-120VAC, 200-240VAC, 380-415VAC, 440-480VAC

Aux Supply

No Aux Supply, 100-120VAC Aux Supply, 200-240VAC Aux Supply, 380-415VAC Aux Supply, 440-480VAC Aux Supply, 12-24VDC Aux Supply