The problem of Ground lift.
There was a peculiar incidence with a lift during the work of an almost completed multi-storeyed building. The elevator in the building showed signs of malfunctions. There were incidents of elevator buttons not responding properly, stopping on wrong floors. Users were afraid to use the lifts.
The Engineers of the elevator company were baffled by the problem because all systems seemed to be working fine. There was no damaged part, nor the internal logic was wrong. Then they set about looking at grounding system. But even the grounding systems ( Earth pits) were properly done.
They finally found out the issue. There was welding work going on in the building and workers had actually connected the neutral line to Earthing line . Due to this there was lift in ground potential wrt actual ground. This had caused malfunction in the lifts.
Some time there is situations at many sites where two points have different ground potentials. Generally such issues are to be tackled at design stage by means of Earth pits. However some there are sites where such issues crop up even in case of well designed systems. They can also create an electric shock hazard or may be source of noise or interference. This situation is called Ground Lift.
Two ground points at different potential can produce a Ground loop. It there is connection between these two points via any equipment , current will flow and if the current is high then may be hazardous
Ground lift Preventor
GLP is device which senses leakage voltage between neutral and ground and gives a signal which can be given to relay or contactor to cut off the supply to the system thereby saving it from possible damages.
GLP can be beneficial various areas.
- Medical equipments
- Control panels
- Industrial equipments like CNC machines.
- Automation equipments like PLC panels
- Elevators and Escalator
Technical specifications of GLP
|System Voltage:||230V AC 50Hz|
|Supply Voltage range:||180V AC – 250V AC|
|Supply Current:||< 10mA|
|Auxillary Supply:||Not Required|
|Relay Contact:||5A Potential free. (COM-NO-NC)|
|Relay On at Reset or Power On
Relay Off at Ground Lift
|Indications:||Mains On – Green LED
Grounded – Red LED
|Mounting:||DIN Rail or Chassis Mounting|
|Dimensions:||45mm X 76mm X 114mm|
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