[PSES] Meaning of MSPD

Tue, 19 Sep 2017 02:15:08 -0700

Good point John, I did explain MSPD meant Multi-service Surge Protective Device in an earlier message, but I should have repeated that for new readers.
Surge Protective Devices (SPDs) tend to be customised to the service they are intended to protect. Power service SPDs can be classified into AC SPDs such as used for AC mains overvoltage limiting and DC SPDs for DC overvoltage limiting such as used for Photo-Voltaic (PV) systems. Signal service SPDs serve a plethora of services such as RS 432, Plain Old Telephone Service (POTS), Ethernet and xDSL (all types of Digital Subscriber Line) Many pieces of equipment will have at least a power service and a signal service (Power over Ethernet (PoE) has both power and signal in the one feed). 


In spite of IEC SC 37A discussing MSPDs for nearly ten years a 
definition has yet to appear in the IEC Glossary. You have to look 
elsewhere for a definition:


IEEE Std. C62.50-2012

multiservice (multiport) surge protective device (MSPD): A surge 
protective device providing protection of equipment connected to two or 
more services such as power, telecommunications, signaling, data, etc., 
with the respective conductors routed via a common enclosure in which an 
internal shared ground reference bond has been provided among these 
services during surge conditions.


IEEE Std 1100-1992

surge reference equalizer: A surge protective device used for connecting 
equipment to external systems whereby all conductors connected to the 
protected load are routed, physically and electrically, through a single 
enclosure with a shared reference point between the input and output 
ports of each system.


ITU-T recommendation K.85

multiservice surge protective device (MSPD) : A surge protective device 
(SPD) containing both telecommunications and mains protection. It may 
also include port protection for video or Ethernet.



The ITU-T definition needs improvement because it omits the most 
important MSPD feature that the SPDs for the different sevices have "an 
internal shared ground/earth/PE reference bond"



The MSPD is great for the equipment it protects, but the unexpected 
consquence is the surge on one service can transfer to another service, 
via the MSPD, if the PE bonding wiring inductance is significant.



Regards,

Mick Maytum

Safety and Telecom
Standards

[email protected]



------ Original Message ------
From: "John Woodgate" <[email protected]>
To: "mickm" <[email protected]>; [email protected]
Sent: 19/09/2017 09:16:50
Subject: RE: [PSES] power strip details


Good info. What is an MSPD?

With best wishes DESIGN IT IN! OOO – Own Opinions Only
www.jmwa.demon.co.uk J M Woodgate and Associates Rayleigh England

UK is a sovereignty, not a Zollverein-ty

-----Original Message-----
From: mickm [mailto:[email protected]]
Sent: Tuesday, September 19, 2017 8:51 AM
To: [email protected]
Subject: [PSES] power strip details


IEEE Std. C62.41.1 (2002 - reaffirmed 2008) contains a mountain of 
information. If you go to A.2.2.3 Voltages induced in cables adjacent 
to down-conductors, it covers the induced voltage in an open-circuit 
loop by a nearby lightning current. The induced voltage table gives 
values ranging from 50 V to 500 V. Do the same calculation for Ethernet 
cables and you end up with voltages in the kV region. The inclusion of 
a voltage limiter is not covered. The poor coupling between the source 
and victim means that the voltage limiter current is surprisingly 
small.



My previous comments are comprehended with statements like "The 
resulting voltages induced in the loop by the fast-changing surge 
currents flowing in the grounding system can cause a large voltage 
difference between the power port and the telecommunications port".
Hence paving the way for the use of MSPDs to reduce the inter-service 
voltage differences for equipment or equipment clusters.



At the time of document creation, MSPDs where not widely used and in 
Annex D called "surge reference equalisers". To understand how the MSPD 
transfers the surge on one service to another you need to look at more 
modern documents like ITU-T recommendation K.98 (08/2014) Overvoltage 
protection guide for telecommunication equipment installed in customer 
premises. This Recommendation covers direct strikes to the incoming 
service feed, mains configuration types of TN-S, TN-C, TN-C-S, TT and 
IT together with effects of various earthing system lead lengths and 
earth electrode resistances.



Time is running out for IEEE Std. C62.41.1, under new IEEE rules the 
life of a standard is 10 years. If nothing is done to revise C62.41.1 
it with be withdrawn in 2018. Hopefully the IEEE PES Surge Protective 
Device Committee will take up this challenge and, as part of the 
revision rational,  replace the 10/350 with the more realistic values 
from CIGRÉ Technical Bulletin (TB) 549 (2013) Lightning Parameters for 
Engineering Applications



Regards,

Mick Maytum

Safety and Telecom
Standards

[email protected]

https://ictsp-essays.info


------ Original Message ------
From: "Richard Nute" <[email protected]>
To: [email protected]
Sent: 18/09/2017 18:58:00
Subject: Re: [PSES] power strip details


Hi Ralph:


Thanks for the reference.  My comments are validated by ANSI C62.41.1 
.


Best regards,
Rich


-----Original Message-----
From: Ralph McDiarmid [mailto:[email protected]]
Sent: Monday, September 18, 2017 9:01 AM
To: [email protected]
Subject: Re: [PSES] power strip details

Pardon me, the correct reference is ANSI C62.41.1  (finger trouble on
keyboard)

Ralph McDiarmid
Product Compliance
Engineering
Solar Business
Schneider Electric


-----Original Message-----
From: Ralph McDiarmid
Sent: Monday, September 18, 2017 8:55 AM
To: [email protected]
Subject: RE: [PSES] power strip details

While I agree that an SPD at the service entrance seems to be the way
to suppress surges resulting from direct/near/far lightning strokes,
ANSI C62.4.1 writes about switching transients on circuits which cause

oscillatory surges on the mains.  SPD at service entrance might be 
less

effective for those.  The ANSI standard seems a very good summary of
what is a complex topic.

Ralph McDiarmid
Product Compliance
Engineering
Solar Business
Schneider Electric


From: Richard Nute [mailto:[email protected]]
Sent: Saturday, September 16, 2017 12:30 PM
To: [email protected]
Subject: Re: [PSES] power strip details


I believe the principal culprit is the extreme magnetic field that
surrounds the conductors when the surge protector operates rather than

the current in the PE conductor.  This field can generate high 
voltages

in adjacent and nearby low-voltage conductors such as telephone and
data cables.  Think air-core transformer.

If the surge protector is at the service entrance, then the high
current is in the electricity supplier wires, and the coupling to
telephone, cable, and data cables is reduced due to the distance
between the wires.

http://www.nemasurge.org/faqs/

Rich


From: mickm [mailto:[email protected]]
Sent: Saturday, September 16, 2017 1:40 AM
To: mailto:[email protected]
Subject: [PSES] power strip details


John,
   It seems to me that TC 108 documents really devise surge protection
component tests rather that complete equipment tests and so miss some
hidden field gotchas.


I with Richards point about surge protection, for me the concern is 
the
surge current being diverted into the PE system creating local PE 
surge

differential voltage rises.
Multi-service surge protective devices (MSPDs) - all in one surge
protection (mitigation actually) - can cause problems here by
transferring a surge on one service, say AC mains, to another service
e.g. telephone service, because that service feed offers a better path
for the diverted surge current than the PE connection.
Equipment connected to the protected output of the MSPD should survive
the surge, but equipment connected on the unprotected side may suffer
due to the unexpected diverted surge. Solution, put and MSPD on every
bit of equipment. Looks like a win-win situation for MSPD
manufacturers.


Regards,
Mick Maytum
Safety and Telecom
Standards
mailto:[email protected]
Ictsp-essays.info

------ Original Message ------
From: "John Woodgate" <mailto:[email protected]>
To: mailto:[email protected]
Sent: 16/09/2017 08:04:59
Subject: Re: [PSES] power strip details

I agree, but doesn't that also apply to surge-suppression built into
equipment?  Should we stop requiring surge immunity testing on
equipment?

With best wishes DESIGN IT IN! OOO – Own Opinions Only
http://www.jmwa.demon.co.uk/ J M Woodgate and Associates Rayleigh
England

UK is a sovereignty, not a Zollverein-ty


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