Download The proposal seems to consider power contact with commercial

TR41.7.1_03-02-006_(Power Contact Proposal Draft)
TR41.7_03-02-004_(TR41.7.1-Power Contact Proposal Draft)
To: Bill Bryans
cc: Tom Burke, Rich Pescatore, Tom Killam
From TR41.7
Discussed in TR41.7.1 agreed to by TR41.7 approved by TR41.
Agree in principle to the addition of power contact requirements to IEC60950.
The proposal only considers power contact with commercial power secondary mains
distribution. In North America we are also concerned with interaction of primary power
distribution systems with the TELECOMMUNICATIONS NETWORK.
Based on its covering only secondary power contact issues, the proposal is not less severe but
is incomplete with respect to the power fault environment that the testing done in the USA and
Canada covers.
A note should be added to 6.4.1 after the first paragraph (line 91) as follows:
Note 1: These requirements address contact between secondary power distribution systems
and TELECOMMUNICATIONS NETWORK conductors and do not cover the interaction (i.e.
contact, induction, etc.) between primary power distribution systems and
TELECOMMUNICATIONS NETWORKS.
Note 2: In the USA and Canada, additional requirements addressing primary distribution power
interaction apply.
Under section 3 “Rationale”, line 57 it is stated that the source voltage should equal the local
mains supply. Clause 6.4.1 lines 100 and 114 should reflect the worst-case nominal voltages
that may be encountered in different areas around the globe.
Recommend changing the test voltage to 240V.
Also, add the following note:
Note: Where the above voltages do not represent the local mains supply, the nominal voltage
of the local mains should be considered.
We are not familiar with the rationale in K44 concerning the line and contact impedance
estimates. Generally in NA the fault current path in a secondary power distribution fault to
communications systems is considered to be of relatively low impedance. In addition, low
current faults that are known to occur are covered during the testing associated with primary
distribution power contact testing (L3, L4). An “in some countries note” should be added after
line 115 to take into account the additional testing performed in NA.
Note: In the US and Canada, the test is conducted with an open circuit voltage of 120 or 240 V
and a short circuit current of 25A. Low current testing is addressed as part of the primary
distribution power evaluation.