Subject: [TICTOC] Requirements draft - call for assistance/power systems

From: "STUART VENTERS" <[email-masked]>
Date: Mon, 22 Sep 2008 09:41:15 -0500

Pat, (or any power expert listening)

For power system timing requirements, any idea what sort of accuracy is desired or in common practice?

Without clues, as a starting point, my guess would be some combination of the following:

1) For correlating meter readings across the grid for billing purposes.
    (Perhaps 1 second would be good enough for this?)

2) For correlating significant events (like breaker trips) over the grid to aid in determining the root cause of a failure.  (Perhaps 1 to 10 mS would be good enough for this?)

3) For correlating voltage and current phase angles over the grid.  (At 60Hz, 4.6 uS would be 1/10 of a degree?)

But it seems like we should have some additional clues as to if these numbers are reasonable and if these or other applications are what is actually needed before adding specific requirements

Also, what sort of packet network would it need to maintain the accuracy over.  (On a LAN inside the substation, outside over a dedicated link, other?)

Regards,

Stuart

-----Original Message-----

----------------------------------------------------------------------

Message: 1
Date: Thu, 18 Sep 2008 00:44:01 -0700
From: [email-masked]
Subject: Re: [TICTOC] Requirements draft - call for assistance
To: Yaakov Stein <[email-masked]>
Cc: "[email-masked]" <[email-masked]>
Message-ID:
	<[email-masked]>
	
Content-Type: text/plain; charset=US-ASCII

Hi Yaakov,

I can comment on the electric power and instrumentation bit. Each power
grid sub-station has a large number of monitoring devices. These devices
historically have been served time via IRIG-B distributed time systems. The
substations will typically have a gps receiver for time and 1pps to drive
the IRIG generators. the backhaul networks are usually private circuit
based networks. In past years many of these were on SNA or some other
similar network. As these substations are upgraded they are being
implemented with local LAN's and will have time distribution systems based
on 1588 or ntp. This allows the removal of the IRIG systems. The backhaul
networks can then be migrated to packet based with whatever access makes
sense for each location. The time distribution systems are local to the
substations.

In test and measurement the LXI forum, LAN extensions for Instrumentation,
has mandated the use of 1588 for compliance. Again this is a local time
distribution paradigm with a local time source.

Many of the "time" based event correlation systems use a local source of
time, typically gps, for time stamps. This is then sent in non-real time to
the monitoring systems for overall system correlation processing. I agree
with your thought that most of these are not applicable to the TICTOC work.

Hopefully this info is helpful.

Pat
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TICTOC mailing list
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https://www.ietf.org/mailman/listinfo/tictoc

---

From: [email-masked]
Date: Mon, 22 Sep 2008 08:20:38 -0700

Hi Stuart,

The goal of time correlation accuracy in sub-stations for power 
distribution systems is 1uS. Across power distribution networks per power 
generating station is 10uS. These goals are the targets defined by EPRI, 
Electric Power Research Institute. In reality the needs for correlation 
come down to as Stuart says looking at the slope of the change. The goal 
is to identify the voltage event. The frequency is derived from the 
rotation of the armature in the power plant. Quick and sudden changes in 
voltage drop across distribution environments are the real tough ones to 
spot before the become breaker trips.
The networks used are almost always private. They are mostly SNA types 
many over frame relay with spoofing routers at the end points.  As you can 
imagine the post event processing is almost useless in regards to 
intelligent power grid "self healing" grids.

The use of the public internet to carry this mission critical data is not 
going to happen given todays operating paradigms.

Regards,

Pat

"STUART VENTERS" <[email-masked]> 
09/22/2008 07:41 AM

To
<[email-masked]>
cc
<[email-masked]>
Subject
[TICTOC] Requirements draft - call for assistance/power systems

For power system timing requirements, any idea what sort of accuracy is 
desired or in common practice?

Without clues, as a starting point, my guess would be some combination of 
the following:

2) For correlating significant events (like breaker trips) over the grid 
to aid in determining the root cause of a failure.  (Perhaps 1 to 10 mS 
would be good enough for this?)

3) For correlating voltage and current phase angles over the grid.  (At 
60Hz, 4.6 uS would be 1/10 of a degree?)

But it seems like we should have some additional clues as to if these 
numbers are reasonable and if these or other applications are what is 
actually needed before adding specific requirements

Also, what sort of packet network would it need to maintain the accuracy 
over.  (On a LAN inside the substation, outside over a dedicated link, 
other?)

Regards,

Stuart

-----Original Message-----

Message: 1

Hi Yaakov,

historically have been served time via IRIG-B distributed time systems. 
The

Many of the "time" based event correlation systems use a local source of
time, typically gps, for time stamps. This is then sent in non-real time 
to
the monitoring systems for overall system correlation processing. I agree
with your thought that most of these are not applicable to the TICTOC 
work.

Pat

---

From: "Doug Arnold" <[email-masked]>
Date: Wed, 24 Sep 2008 20:08:32 -0700

I have also heard the 1us number for substations.  Substations are
relatively small, engineered networks.  Probably the 1us can be met by
PTP, with the default profile, and some guidelines about network design,
including the recommended use of transparent clocks or boundary clocks
for switches.  This is very important, but I don't see a role for the
IETF.
 
I have heard another requirement, which is more relevant to the IETF.
That is a requirement for 1 ms timing accuracy, CONSISTENTLY, across the
communications infrastructure of regional power grids.  Such a grid
might contain several SONET rings, as well as Ethernet and numerous
routers in the path between master and slave.  1 ms sounds easy, except
the power utility would want to count on it.  Besides a lot of queuing
delay variation, such networks likely have large asymmetries.  Neither
NTP, nor PTP can meet this spec consistently without the the "on path
support" (whatever that turns out to be) which TICTOC promises.  
 
//Doug Arnold

________________________________

From: [email-masked] [mailto:[email-masked]] On Behalf
Of [email-masked]
Sent: Monday, September 22, 2008 8:21 AM
To: STUART VENTERS
Cc: [email-masked]
Subject: Re: [TICTOC] Requirements draft - call for assistance/power
systems

Hi Stuart, 

The goal of time correlation accuracy in sub-stations for power
distribution systems is 1uS. Across power distribution networks per
power generating station is 10uS. These goals are the targets defined by
EPRI, Electric Power Research Institute. In reality the needs for
correlation come down to as Stuart says looking at the slope of the
change. The goal is to identify the voltage event. The frequency is
derived from the rotation of the armature in the power plant. Quick and
sudden changes in voltage drop across distribution environments are the
real tough ones to spot before the become breaker trips. 
The networks used are almost always private. They are mostly SNA types
many over frame relay with spoofing routers at the end points.  As you
can imagine the post event processing is almost useless in regards to
intelligent power grid "self healing" grids. 

The use of the public internet to carry this mission critical data is
not going to happen given todays operating paradigms. 

Regards, 

Pat

09/22/2008 07:41 AM 

To
<[email-masked]> 
cc
<[email-masked]> 
Subject

Without clues, as a starting point, my guess would be some combination
of the following:

Regards,

Stuart

-----Original Message-----

Message: 1

Hi Yaakov,

I can comment on the electric power and instrumentation bit. Each power
grid sub-station has a large number of monitoring devices. These devices
historically have been served time via IRIG-B distributed time systems.
The
substations will typically have a gps receiver for time and 1pps to
drive
the IRIG generators. the backhaul networks are usually private circuit
based networks. In past years many of these were on SNA or some other
similar network. As these substations are upgraded they are being
implemented with local LAN's and will have time distribution systems
based
on 1588 or ntp. This allows the removal of the IRIG systems. The
backhaul
networks can then be migrated to packet based with whatever access makes
sense for each location. The time distribution systems are local to the
substations.

In test and measurement the LXI forum, LAN extensions for
Instrumentation,
has mandated the use of 1588 for compliance. Again this is a local time
distribution paradigm with a local time source.

Many of the "time" based event correlation systems use a local source of
time, typically gps, for time stamps. This is then sent in non-real time
to
the monitoring systems for overall system correlation processing. I
agree
with your thought that most of these are not applicable to the TICTOC
work.

Pat