CoGen NG Turbine

[infinity]

Have a 200kw natural gas CoGen turbine used to generate electricity and to heat water with a heat exchanger via the turbine exhaust. The turbine uses a 480/277 volts output to a disconnect switch mounted on the wall within sight. The disonnect is wired with the turbine output to the "load" side of the disconnect (fuses). This means that with the disconnect OFF and the turbine running that the fuses are energized. Since the line side of this disconnect is connected to a switchboard the switch has two sources of power.

The manufacturer has stated that this is code compliant. We would like an auxiliary switch within the disconnect to shut down the turbine when the disco is opened. We're being told that it's not required. Anyone have any thoughts or code issues with this setup?

 

[augie47]

Have you looked at 404.6 (C) Exception ?

 

[infinity]

I'm without my book at the moment.

 

[don_resqcapt19]

If you close the switch with the turbine supplying power, how do you sync it with the panel on the "supply side" of the disconnect?

 

[augie47]

(C) Connection of Switches. Single-throw knife switches and switches with butt contacts shall be connected such that their blades are de-energized when the switch is in the open position. Bolted pressure contact switches shall have barriers that prevent inadvertent contact with energized blades.
Single-throw knife switches, bolted pressure contact switches, molded case switches, switches with butt contacts, and circuit breakers used as switches shall be connected so that the terminals supplying the load are deenergized when the switch is in the open position.
Exception: The blades and terminals supplying the load of a switch shall be permitted to be energized when the switch is in the open position where the switch is connected to circuits or equipment inherently capable of providing a backfeed source of power. For such installations, a permanent sign shall be installed on the switch enclosure or immediately adjacent to open switches with the following words or equivalent: WARNING? LOAD SIDE TERMINALS MAY BE ENERGIZED BY BACKFEED.

 

[infinity]

If you close the switch with the turbine supplying power, how do you sync it with the panel on the "supply side" of the disconnect?

The sales rep said that it will sync automatically.

 

[eHunter]

The sales rep said that it will sync automatically.

Sounds interesting...
What brand NG turbine are you working with?
Have any pics?

 

[infinity]

(C) Connection of Switches. Single-throw knife switches and switches with butt contacts shall be connected such that their blades are de-energized when the switch is in the open position. Bolted pressure contact switches shall have barriers that prevent inadvertent contact with energized blades.
Single-throw knife switches, bolted pressure contact switches, molded case switches, switches with butt contacts, and circuit breakers used as switches shall be connected so that the terminals supplying the load are deenergized when the switch is in the open position.
Exception: The blades and terminals supplying the load of a switch shall be permitted to be energized when the switch is in the open position where the switch is connected to circuits or equipment inherently capable of providing a backfeed source of power. For such installations, a permanent sign shall be installed on the switch enclosure or immediately adjacent to open switches with the following words or equivalent: WARNING? LOAD SIDE TERMINALS MAY BE ENERGIZED BY BACKFEED.

Thanks Augie, so all that we need is a few signs.

Sounds interesting...
What brand NG turbine are you working with?
Have any pics?

Two of these, one 65 KW and one 200 KW.

http://www.capstoneturbine.com/

 

[eHunter]

Thanks Augie, so all that we need is a few signs.




Two of these, one 65 KW and one 200 KW.

http://www.capstoneturbine.com/

Thanks, I am very familiar with Capstone.
They are about the only manufacturer of smaller capacity cogen gas turbine units.
Are these fully enclosed or open units?
Do you happen to know if these are recently manufactured units?
The older units were fairly noisey in operation.


We provide contract support for the military and another goverment agency and a stipulation of our contract is to have a 12 hour mean time to restore service on a series of Solar gas turbine plants. Consequently we have a Saturn 20 and a Mercury 50 in our warehouse. Both are packaged in large shipping containers on steroids.

http://mysolar.cat.com/

 

[don_resqcapt19]

The sales rep said that it will sync automatically.

Is this a standard disconnect switch? If so there is no way that you can have auto sync if both sides of the switch are live when you operate the switch.

 

[infinity]

Is this a standard disconnect switch? If so there is no way that you can have auto sync if both sides of the switch are live when you operate the switch.

Yes, standard 3 pole disconnect switch. Rep insists that it will "auto sync". Maybe we will let him throw the switch. hmy:

 

[don_resqcapt19]

Yes, standard 3 pole disconnect switch. Rep insists that it will "auto sync". Maybe we will let him throw the switch. hmy:

If both sides of the switch are energized, how is auto sync possible? Are there other devices between the utility and the turbine that would make it always run in sync with the utility?

 

[eHunter]

If both sides of the switch are energized, how is auto sync possible? Are there other devices between the utility and the turbine that would make it always run in sync with the utility?

Utility or parallel synchronization and protective relaying is integrated into the Capstone turbine generation control package.
There are other control and sense leads besides the output leads that allow the Capstone units to sync to a source where that may be the utility or another generator or power producing unit such as an inverter.