Communication closet grounding
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Re: Communication closet grounding
Not very much detailed info supplied by obo .
Unless this is a SDS, and even then the grounding does get back to the building service grounding system, I would think 250.4 and 250.58 would require the Communications Closet equipment to be, ultimately , grounded to the building grounding system.
Not very much detailed info supplied by obo .
Unless this is a SDS, and even then the grounding does get back to the building service grounding system, I would think 250.4 and 250.58 would require the Communications Closet equipment to be, ultimately , grounded to the building grounding system.
Re: Communication closet grounding
OBO, is this an equipment ground, signal ground, or discharge ground?
An equipment ground will originate from the grounded conductor to ground bonding point. Example would be a DC power plant, isolation transformer, or service entrance.
A signal ground can come from the same point as equipment ground preferable or from the building ground electrode system.
A discharge ground will originate from the building ground electrode system.
Cannot help you unless you are very specific.
[ May 25, 2003, 07:08 PM: Message edited by: dereckbc ]
OBO, is this an equipment ground, signal ground, or discharge ground?
An equipment ground will originate from the grounded conductor to ground bonding point. Example would be a DC power plant, isolation transformer, or service entrance.
A signal ground can come from the same point as equipment ground preferable or from the building ground electrode system.
A discharge ground will originate from the building ground electrode system.
Cannot help you unless you are very specific.
[ May 25, 2003, 07:08 PM: Message edited by: dereckbc ]
Re: Communication closet grounding
Sorry about the confusion, I'm not an electrical engineer so I'm not familiar with the terminology. I'll try to be more specific.
Communication equipment grounding serves two main purposes, one is to protect in case of electrocution and the second one is to reduce noises.
In our communication rooms, the chassis of each network element is grounded to the room's power board with a designated cable (yellow/green). The communication equipment and the power board are a few feet away.
The power board itself is grounded through the main power lines that are coming from the energy center.
I have read somewhere that it's preferable to separate the AC ground bar and the equipment ground bar, to avoid noises, is this true?
I think however that I got the answer from dereckbc
Sorry about the confusion, I'm not an electrical engineer so I'm not familiar with the terminology. I'll try to be more specific.
Communication equipment grounding serves two main purposes, one is to protect in case of electrocution and the second one is to reduce noises.
In our communication rooms, the chassis of each network element is grounded to the room's power board with a designated cable (yellow/green). The communication equipment and the power board are a few feet away.
The power board itself is grounded through the main power lines that are coming from the energy center.
I have read somewhere that it's preferable to separate the AC ground bar and the equipment ground bar, to avoid noises, is this true?
I think however that I got the answer from dereckbc
Re: Communication closet grounding
OBO, this is difficult to explain on the forum.
Is your equipment DC powered or AC powered??
If it is AC powered you use the techniques outline by NEC article 250. The grounds serve a one main purpose and that is to clear a fault and operate the OCPD.
If it is DC powered (by a battery/rectifier plant) the techniques are some what different, but similar. The equipment frame grounds only purpose is to clear faults as AC powered equipment. The main difference is the EGC is not typically run with the battery conductors and are larger to overcome the lower voltages and long distances encountered.
There are sometimes other ground conductors used by the equipment. One is what is called a discharge ground. The discharge ground is used terminate surge protectors, cable protectors, and cable shields. Normally these conductors do nothing until an inside/outside plant cable is struck by lightning or comes in contact with high voltage. At that point the surge arrestors operate and discharge the energy to ground via its dedicated conductor. By using a dedicated conductor any faults are routed around any sensitive equipment.
Another type of ground is what is called a logic or signal ground. This ground is used to reference the various signal receivers used in telecom equipment. Again this is dedicated ground used for only one dedicated purpose. This is what is sometimes known as a low noise ground, but that is really a myth because any length of wire exhibits a high impedance at the higher frequency?s and acts like an antenna.
The trick is originating any type of ground (except GEC and discharge) from the power source be it whatever like a DC power plant, isolation/step-down transformer, or AC service entrance. They originate from the main bonding point to the grounded circuit conductor if used.
What is important is that all the grounds are bonded together. Typically in a phone office this point is call the Office Principle Ground Point Bus (OPGPB). The OPGPB is a bus bar where all the ground electrodes are terminated too in a radial fashion to form a low impedance connection to earth at low frequencies (not possible to have low impedance connections at high frequencies using cable). Then from the OPGPB all the grounds are fed out radially via dedicated conductors to the various systems like AC service entrance, DC plants, discharge devices, SDS, signal/logic, raised floor grids, etc.
OBO, this is difficult to explain on the forum.
Is your equipment DC powered or AC powered??
If it is AC powered you use the techniques outline by NEC article 250. The grounds serve a one main purpose and that is to clear a fault and operate the OCPD.
If it is DC powered (by a battery/rectifier plant) the techniques are some what different, but similar. The equipment frame grounds only purpose is to clear faults as AC powered equipment. The main difference is the EGC is not typically run with the battery conductors and are larger to overcome the lower voltages and long distances encountered.
There are sometimes other ground conductors used by the equipment. One is what is called a discharge ground. The discharge ground is used terminate surge protectors, cable protectors, and cable shields. Normally these conductors do nothing until an inside/outside plant cable is struck by lightning or comes in contact with high voltage. At that point the surge arrestors operate and discharge the energy to ground via its dedicated conductor. By using a dedicated conductor any faults are routed around any sensitive equipment.
Another type of ground is what is called a logic or signal ground. This ground is used to reference the various signal receivers used in telecom equipment. Again this is dedicated ground used for only one dedicated purpose. This is what is sometimes known as a low noise ground, but that is really a myth because any length of wire exhibits a high impedance at the higher frequency?s and acts like an antenna.
The trick is originating any type of ground (except GEC and discharge) from the power source be it whatever like a DC power plant, isolation/step-down transformer, or AC service entrance. They originate from the main bonding point to the grounded circuit conductor if used.
What is important is that all the grounds are bonded together. Typically in a phone office this point is call the Office Principle Ground Point Bus (OPGPB). The OPGPB is a bus bar where all the ground electrodes are terminated too in a radial fashion to form a low impedance connection to earth at low frequencies (not possible to have low impedance connections at high frequencies using cable). Then from the OPGPB all the grounds are fed out radially via dedicated conductors to the various systems like AC service entrance, DC plants, discharge devices, SDS, signal/logic, raised floor grids, etc.
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