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Can someone share the let-through curves for GE Current Limiting Fuses GF8B class L (800A to 2000A) In addition I would like to ask how we can accurately read the logarithmic scale for the intermediate values for these let through curves. Thanks

200hp, 480V motor tripping on instantaneous RS510 DigiTrip unit. Motor winding Insulation resistance above 50G-ohm and healthy winding resistance. Trip Unit is healthy and no issue with the cable. What else can cause this? Note: Motor runs for 20-25 min before tripping.

We have an oil leak from GE AK-5A-75 breaker. The oil is leaking from the Gear Reduction Unit coupled to charging motor. We need to refill this but the manual says the type of oil is similar to Atlantic Refining Company Grade HFS#3. Can anyone share the data sheet for this type of oil or...

I want to use it to protect the motor. Since these protections are pretty sensitive so as per my understanding the fault will not wait to reach to a level of actual ground fault but will trip on some percentage of FLA unbalance. I will be using AB E3 or E1 plus relay with Jam/Ground Fault...

We have some critical 20hp motors. The motor starters have a MCP (motor circuit protector), NEMA Contactor and bi-metallic overload relay without any ground fault protection. I want to change the bimetallic overload relay with electronic overload relay that comes with ground/jam protection...

We have Seven large synchronous motors rated 23000hp with ABB Unitrol F excitation System. The motors are running with VAR control, Auto mode. on the Unitrol Control Panel, there is a percentage set point. This set point is called as "Reference Value" in ABB documentation. Usually, this...

I believe you had an under voltage dip on side A. Standard MCCs use control power from the line side connected CPTs, so the under voltage caused the contactors to dropout. the transfer was an open transition transfer and that time was enough to drop the contactors. You need to have voltage dip...

A single phase fault in a 480V MCC led to 3-phase flashover. This flashover caused some other equipment to trip on Overvoltage on 480V switchgear feeding the MCC that experienced flashover. Can flashover in MCC cause overvoltage spikes upstream in 480V switchgear?

Can anyone provide me with the technical literature for Westinghouse BF84F relays 120/110V AC. The datasheets I have do not mention dropout and pick up voltage for the coil.

We have westinghouse BF84F contactor relay in one of the cabinet of a very critical system. The contactor have dual 115Vac input, primary source is energizing the coil and NO contacts whereas secondary source is connected to NC contacts of the contactor. In case of primary power failure, the...

How about using Banana sockets on the breaker control compartment. Is it safe or it voilates any standard?

Greetings, I want to wire some of the breaker signals (breaker status, position, trip and close circuit)to a door mounted plug, so one side of the plug will be wired to the signal and the other side will go to the interface. Can anyone suggest me any suitable and decent looking control plug...

If you have line and bus VTs, you can know if your Line side is actually OFF or its blown fuse. Transfer scheme shall look at both Line and Bus voltages.

I would suggest you to use 1500:1A CT. You cannot do anything to the primary due to the feeder rating but since your relay is 400ft away, i would suggest to use 1A secondary. This will improve things.

This depends on your application and type of equipment. For large size equipment, usually there are primary and backup protection. For example, for a 20MVA transformer, you will have transformer differential and overcurrent protection. Transformer differential will be the primary protection and...

Greetings, Can anyone confirm if there is clock function in GE MM-II relay. We have this relay on a motor feeder and it store just one last event but there is no time for the event. Also in the manual i could not find date and time. The software have for MM-II has installation problems. Thanks

Yes it is ok technically. Only issues are obviously the cost of these CTs and also you need to check the dimensions of these CTs if you have enough space to install them for your application.

Pick-up is always minimum in terms of time and you will need to calculated a voltage accross relay resistor that results due to external faults, so your relay can ride through external faults. So whats the advantage of using a high impdennce differential if you are going to compromise on CTs. Go...

Skogskurra / jreaf 435 was connected just to see the input voltage because we had swells and dips event recorded by the DCS on the output of the UPS (without any trip, only alarms. A 480V switchgear is feeding multiple MCCs and one of those MCC in turns feed the UPS. Another MCC on the same...

We are facing issues with our 90kVA UPS which is more than 25 years old. We connected Fluke 435 to the output of the inverter which recorded multiple events of Dips and Swells. We shifted the Fluke 435 to 480VAC UPS input side and recorded more than 6000 transients events on the fluke within 24...