Voltage Protection for 2000IVS Station Card Ports

[libellis]

We need to provide primary protectors on an outside plant cable that connects digital and analog stations to a 2000IVS. Primary protectors come in various voltage limiting levels with 75V, 100V and 235V being the mix of standard available levels that seem most suitable to choose from. In particular:

1. Digital stations (DTerm Series E) are connected to ports on PN-2DLCB Long Line Station Cards. Would a 75 volt clamping level be the best choice for this case?

2. Analog stations are connected to ports on PN-4LCD-A cards. Would 100 volts or 235 volts be the best choice for this case? I'm not sure what peak ringing voltage is reached on the PN-4LCD-A.

Ideally it would be convenient to use just one type of protector - would 100 volts or 235 volts also work for the digital station ports and protect the stations as well?

 

[belevedere]

Multiline stations operate off of -24 ~ -27 vdc.
Analog trunks are at -26 ~ -52 vdc with a ring voltage around 90 vac
Analog stations are at -27 ~ -48 vdc with 70 ~ 90 vac ring voltage.
Typically lightning protection is placed on the incoming analog trunks and not on the stations.

 

[libellis]

At the distance the cable runs outside between buildings the Electrical Code requires use of protectors. Equally important is that over the years station ports and entire cards connected to this cable have failed (you might ask so why wasn't protection placed years ago, but don't ask). Station ports on other cables at this site which are not outside have not failed, nor have they failed at another site which has long cable runs entirely within buildings. I believe the Long Line Digital Card creates approx. 48v rather than 24v - 27v and I just wanted to be sure that a 75v protector wouldn't be too low a threshold or that a 100v protector wouldn't be too high. For the analog stations, it seems that 235v would be the safer choice.

 

[belevedere]

The long loop cards do boost power. I'll assume that you went through the usual safeguards with grounding the outside cable. The question is how much voltage is getting through and is it less that your proposed 235v protection. I'd lean towards the 75v or 100v threshold.

 

[libellis]

The cable was installed by someone a very long time ago. There is likely some correlation of failures with lightning - the station locations are in a structure exposed to hits and protection should have been provided a long time ago as well. We decided on 75v protectors for the long line digital ports because the next lowest increment is 39v, which is too low given the 48v output level, but high enough to give a safe margin while still providing protection. For the analog ports we were a bit concerned about the 90V peak being too close to 100V so we'll opt for 235v. If that proves to be a poor choice we'll change. Analog station cards are still available on the secondary market, but long line digital cards are hard to come by. Thanks for the input.

 

[OzzieGeorge]

Bear in mind that if you are using message wait, the voltage will get close to the 100v level!

 

[libellis]

We chose 235v for the analog ports - protectors are on order.