Substation Telecommunications DC Bus Protection
Substation Telecommunications DC Bus Protection
(OP)
Can harmful voltage spikes, due to a substation apparatus operation (i.e. breaker trip/close), result on the load side bus of a dc-dc converter which is supplied by the substation backup batteries?
At our utility, wherever we have a telecommunications tower site within a substation, our current practice is to backup our 48V Telecom bus using our substation backup batteries through a dc-dc converter . The Western Electricity Coordinating Council(WECC) doesn't recommend this practice [Ref: WECC Guidelines for the Design of Critical Communications Circuits; Section 4.3.1]. We are trying to determine if we really need to change our dc backup arrangement.
For any of you who have a similar telecom battery backup arrangement, have you experienced any harmful transient voltages on the telecom side of the converter?
At our utility, wherever we have a telecommunications tower site within a substation, our current practice is to backup our 48V Telecom bus using our substation backup batteries through a dc-dc converter . The Western Electricity Coordinating Council(WECC) doesn't recommend this practice [Ref: WECC Guidelines for the Design of Critical Communications Circuits; Section 4.3.1]. We are trying to determine if we really need to change our dc backup arrangement.
For any of you who have a similar telecom battery backup arrangement, have you experienced any harmful transient voltages on the telecom side of the converter?






RE: Substation Telecommunications DC Bus Protection
A DC-DC converter alone (without batteries on the load side) may not be considered sufficiently reliable for substation communications.
I would also be concerned about transients from lightning strike on the tower getting back in to your substation.
RE: Substation Telecommunications DC Bus Protection
One consideration is the usual DC-station power serving protective relaying is typically ungrounded with ground detectors, where telecomm 48V is often solidly grounded on the positive terminal at the power supply {DC-DC converter in your case.}
Ground-potential rise during faults could conceivably induce noise into the comms gear, in particular where there may inappropriately more than one (non-obvious) bond between station ground mat and comms 48V gear.
Does WECC suggest an isolated battery set dedicated to comms only?
RE: Substation Telecommunications DC Bus Protection
So "critical" refers to protective relaying and remedial action, and the advice applies to non-substation hardened equipment. Who would select non-hardened equipment for this application? This may also have been written before IEEE took up the issue with standards like 1613.
RE: Substation Telecommunications DC Bus Protection
As far as lightning strikes on our towers go, we have them well protected with lightning arrestors and solid grounding.
Busbar: the WECC does indeed recommend a separate DC power system for non sub-hardened communication equipment, however our ISO doesn't address this issue so we're left to our best judgement. We've recently (last 5 years) started the practice of supplying comm equipment from the substation DC. That happened because our substation relays have changed from electromechanical to electronics; therefore, we've had to install substation chargers with so little output ripple that they were also adequate for the communications DC. My job is to determine if our use of a dc-dc converter is good engineering practice. If so, we won't install separate DC supplies. Thanks.
Stevenal: Because of our history of practice, we're trying to decide if we need to retrofit all our affected substations. Thanks for reference to IEEE 1613, I wasn't familiar with it.