Connection between network and standby power

[arisakri]

Hello!

I would like to inform me about wiring between network and standby power (three phase generator driven by diesel engine). Switching between network and standby power with mutual mechanical or electrical locking should be at the output of the MV/LV transformer of after the main circuit breaker on the panel. Any IEEE or IEC standard relevant to the topic

 

[crshears]

Hello arisakri, the normally expected protocol here would be for you to first do your own research, then ask questions about whatever you do not understand; if you find you are unsuccessful or are having difficulties locating the necessary resources, please report your specific issues so the participants here will best know how to respond to your query.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[waross]

It depends.
Most often an automatic transfer switch is located after the main service disconnect.
There are exceptions.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[arisakri]

Hello crshears,

Thank for your reply. I already have done my research. The most common is the ATS is located after the main service disconnect, but i could not find the justification why the do that. Furthermore i could not find a protocol from IEEE or IEC about this topic to use it as guideline.
I will be glad if you suggest me a book/document/paper to describe theses topics.

Thank you in advance

 

[crshears]

The most common is the ATS is located after the main service disconnect, but i could not find the justification why the do that.

It is my understanding that in residential and smaller commercial applications the main service disconnect is the most common device used to readily separate the customer from the supplying utility, and the presence of any intervening device would defeat this purpose. ATS schemes are thus by default installed downstream of main service disconnects.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[waross]

Actually, when I was installing a lot of these, another factor was that I could pull the main disconnect to do the installation.
Putting the ATS ahead of the main disconnect entailed arranging an outage from the utility.
Some installations did not have a suitable main disconnect and a utility disconnect was always a PITA. (Inconvenient)
One factor.
In one small commercial installation, without a main disconnect, One side of the manual transfer switch became the service disconnect.
(In that jurisdictions there was no code.)


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[SolarPrestige]

Schneider Electric have a guide on this topic. Search for Schneider ECT161, part of their Cahiers Technique publications. The basic understanding in this is good, although the relays mentioned are probably superseded now.

 

[FreddyNurk]

Utility standards on what and where to connect to the network would also take precedence, this obviously depends on geographical location and relevant utility.

EDMS Australia

 

[waross]

Most standby systems never connect to the network or grid.
As long as you are never in parallel with the grid there is no issue with the utility.
Most transfer switches are mechanically interlocked to prevent ever going in parallel with the grid.
If you are going in parallel, even for only a few seconds, for a bumpless retransfer, then the utility does get involved.
The complexity and cost both rise rapidly.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[arisakri]

Both network and standby power supplies all loads through the same panel and main circuit breaker. Transformer and diesel generator is side by side.

 

[waross]

Where is your metering?
You must install the transfer switch downstream from the meter or metering transformers.
You should install the transfer switch downstream of a disconnect switch under your control.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Hoxton]

In Great Britain this comes under Engineering Regulation G99 etc. which generally covers generators in parallel with the network

Clause 7.4 covers Switched Alternative-Only Operation
ie no parallel with mains.

The UK utilities still control this, as the first para of 7.4 states:

Under this mode of operation it is not permissible to operate a Power Generating Module in parallel with the Distribution Network. Regulation 21 of the ESQCR states that it is the Generator’s responsibility to ensure that all parts of the Power Generating Module have been disconnected from the Distribution Network and remain disconnected while the Power Generating Module is operational. The provisions of this EREC do not generally apply and the earthing, protection, instrumentation etc. for this mode of operation are the responsibility of the Generator, however, where such Power Generating Module is to be installed, the DNO shall be given the opportunity to inspect the equipment and witness commissioning of any changeover equipment and interlocking.

This is often overlooked by contractors!

There are useful typical schematics. it is a public document. i can upload it if anyone wants a copy