essential and nonessential loads

[144x]

in an AC distribution panel how should the loads be distributed on essential and non essential busbars?basically what are essential and nonessential loads in a substation?should the same loads be distributed on both busbars ?are there any sources on the web?
thanks.

 

[omara]

I would suggest that any load related to protection, switchgear operation, alarm system, recorders, or operator safety would be on the essential bus. E.g. dc chargers, UPS, minimum important lighting. All other loads mey be relegated to the non-essential bus.

 

[cuky2000]

The critical loads are on the auxiliary AC/DC system to operate the substation safely in the event of loss of power ehither locally or remote. Keep in mind that substations is an inportant facility that should have high degree of availability during and after the ocuurence of disaster.

Typicall critical loads are as follow:

1- DC subsystem (Baterry charger, UPS)
2- Communication for protection & voice(SCADA, PLC, radio,etc)
3- Control circuit (lights, relays, microprocessor equipment, mimic panels, etc)
4- Monitoring and supervisoring equipment(printer,GPS, Fault & event recorder,computer & monitor, etc.)
5- Local annuciator and Alarm system.
6- External & Internal lighting.
7- Security system (Intrussion, CCVT, etc)
8- Fire alarm circuits
9- Maintenance receptacle.
10-Other vital equipment if require(HVAC, pump,Motor operate equipment, compressor,etc.)

 

[144x]

Dear cucky2000
so what remains to be tranferred on the nonessential busbar?
the diesel generator does not have enough power to feed all
those loads during emergency.

 

[redtrumpet]

Someday one of us will put this link in a FAQ:

http://www.usda.gov/rus/electric/bulletins.htm

See Bulletin 1724E-300, Chapter 15, AC and DC Auxiliary Systems. Read it and if you still have questions, come back to us.

 

[144x]

what ever you say boss

 

[cuky2000]

Dear 144X,

It is not the intention of the list presented above to suggest connecting all auxiliary loads to the critical bus. What I trying to suggest is a list of common equipment that I believe often is found connected to the essential bus.

I would like to take this opportunity to mention that the philosophy to connect load on the essential bus could be based on the importance of the substation to achieve degree of reliability, availability and maintainability expected.

Comparing the number of equipment connected to the essential load in a typical 69 kV distribution substation and a 500 kV transmission substation, there is substantial differences in number and type of load connected to the essential bus.

Also the power source could vary. For instance, redundancy battery-bank/charger dedicated battery/charger for the communication system, independent AC power sources, stand-by generator, etc.

Please see the list of critical load on listed on page 674 of the reference posted by Redtrumpet for rural substation up to 230 kV.

 

[jbartos]

Suggestion: When it comes to essential loads, there are further ramifications, e.g. emergency loads (life safety, critical branch, etc.) and equipment system loads. The life safety loads are supposed to be on within 10 seconds. There are safety codes, e.g. NFPA 101, 110, 70, etc. related to this topic. Visit

http://www.nfpa.org

for codes and more info.