Surge Arrestors for Line Entries at a Substation

[mersin33]

Hi,

I have been trying to find a source of information for the use of surge arrestors at the line entries at substations, for 230kV lines and above.

All the information I have is regarding the use of SA for transformer protection. Could anybody suggest a source of information for this application?

Regards,

Gokhan

 

[busbar]

Aside from manufacturer’s literature, one reference may be IEEE Std C62.22-1997
Application of Metal-OxideSurge Arresters for Alternating-Current Systems
If you can’t find it in a library, it may be obtained through ieee.org or global.ihs.com

 

[peebee]

The IEEE Color Series (Green Book and Red Book) also have some information.

 

[cuky2000]

The purpose of the surge arrester on the line entrance is to limit the surge overvoltage by a traveling wave originated mainly by lightning strike on the transmission line, switching or fast reclosing.

The effect of the traveling wave could virtually double during reflection on the line. One of the worst-case scenarios is with the line circuit breaker open. An appropriate line arrester will protect circuit breakers and other equipment in the substation exposed to lightning surge.

Beware of the arrester provides protection up to limited distance inside the substation. Some insulation coordination study recommends arrester in addition to the line entrance and transformer or other apparatus.

The only way to determine the need or not have SA protection is using Transient Network Analyzer (TNT) or using a computer model such as EMTP. Since those tools are expensive and not always available, many engineers opts for install arrester on the line side recognizing that the cost of surge arrester are relative inexpensive.

 

[jghrist]

The surge entering the station from the transmission line is limited by the BIL of the line which will be higher than the BIL of the substation. Whether or not you need arresters at the incoming lines depends on the length of bus between the incoming lines and open points (where the surge doubles) and arresters at transformers (where the surge is limited). The voltages due to various reflections can be calculated (with great difficult) using the method of lattice networks described in Chapter 15 of the Westinghouse T&D Reference Book.

Reflections of strokes striking the bus can also be analyzed with this technique. The surge current and voltage for strikes to the bus are limited by shielding. See "IEEE Guide for Direct Lightinig Stroke Shielding of Substation", IEEE Std 998.

 

[dpc]

Breakers have been known to arc over and fail due to voltage transient coming in from overhead lines. Surge protection can help protect against this problem, although most lines don't have it.

 

[peebee]

Be aware that many underground lines are fed by overhead lines further upstream -- don't assume that since your feeder is coming out of the ground that you don't need lightning arrestors.

Also be aware that lightning arrestors are different from transient voltage surge suppressors (TVSS). They perform a similar function but for different voltage and energy levels. If you have a critical application you need both, and perhaps several levels of TVSS protection.

 

[dcdtn]

As a rule, we use surge arresters on our system in front of all SF6 breakers that are 115-kV and above. Not sure about below 115-kV since I don't deal with that much. I once knew the technical reasons why we use SA's primarily for gas breakers and not oil.

 

[RajT]

You may ofcourse use the same SA at the line entries if you wish. The reason however for locating the SA at the transf line terminals is to provide protection to the transf in the event that the upstream CB is open and the lightning strikes the transf bushing.

 

[cuky2000]

Dear RajT:

I’m not convinced with your approach to select surge arrester on the line side. In many projects line arrester is not an option if the investment and reliability of the installation should be maintained.

Surge arrester on the line side typically does not provide protection to transformer regardless the status of the circuit breaker.

For instance, transformer with BIL rated for 650 kV protected with arrester with MCOV rated for 140 kV, the max. Allowable separation (cable length) for single line single transformer is 12 ft (4m). In many design this distance is exceeded.

A universal good rule of thumb is to install surge arrester as closest as practical to the unit to be protected. Many transformers have the SA installed just within few ft to the bushings.

 

[RajT]

Cuky2000,

I do agree with what you say though I did state that it is usual to locate a SA near the transf line terminals (ie its primary bushings)as a must. However I was suggesting that should one wish, then an additional SA may be located at the O/H line gantry to the switchyard which would provide additional protection to the CB in the event that it is open.

 

[neps3]

Hi all

RajT is correct. SAs are installed on the line terminals on the EHV side of the transformers to protect the transformer.

 

[jbartos]

Suggestion to the original posting: Reference:
buff I E E E BOOK™ Published by the Institute of Electrical and Electronics Engineers, Inc. 242™
IEEE Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems IEEE Std 242-2001™ (Revision of IEEE Std 242-1986™)

is important source of information for your application. It states more specific information such as locations of SA and distances from equipment and justify necessity of the SA use, e.g. transformer primary, secondary, etc.

 

[mersin33]

Thanks a lot for all your comments,

There is no doubt about the requirement of a SA connected to trf terminals. I find it interesting that, some utility companies use a SA for their O/H line feeder entries to the substations, yet there is no sound reference to this application. Some of us mentioned IEEE color series. Those books are strictly for commercial and industrial power systems, generally not exceeding 36kV. My question is about transmission systems above 230kV.

Regards,

Gokhan

 

[cuky2000]

Here are some references:

A.R. Hileman "Insulation Coordination" Marcel Dekker, 1999

ANSI/IEEE Std C62.92, See 1.1.2 & 1.1, Appendix A.1

See 1.1.2, 5.17.2 on the work in progress draft of the Std C62.22

http://grouper.ieee.org/groups/spd/Working_Groups/3-4-14/Spring2002/C62-22-2002_dr2.pdf

IEEE Std 1313.2 " Guide for the Application of Insulation Coordination"

IEC Std 71-1 (Part 1 & 2)

http://www.hubbellpowersystems.com/powertest/literature_library/pdfs4lib/OB/EU1426-H.pdf

Clayton & Powell, “Application of Arrester for Complete Lightning Protection of Substation”, AIEE Transaction, Feb 1959.

McNulty, Generalized Study to Determine the Optimum Location of Lightning Arrester in Power Transmission and Sub transmission Stations". Polytechnic Institute of Brooklyn, NY, 1964- A Thesis.

Anderson, "Transmission Line Ref Book-345 kV and Above" EPRI

 

[kyruby]

69kv is the highest voltage I deal with, however, all substation transformers are ordered with station class MOV's mounted on both the high and low side of the transformer. In addition station class MOV's are mounted on the incoming 69kv structure and at the takeoff of the 13.8kv feeder circuits. I would suggest you contact Hubbell/Ohio Brass at 8711 Wadsworth Rd, Wadsworth, OH 44281 about applications. They do have a web site but I don't know the address. Another option is to contact a consulting engineering firm who specializes in substation/transmission design, someone like R.W. Beck. Email me if you would like a contact.

 

[Luis1947]

The purpose of Surge Arresters is to protect the substation equipment. Main equipment is usually the Power Transformer, therefore the proper arrester location should be nearest to the transformer. Arrester will drain surges and the wave profiles along the substation will have suitable values according to the designed insulation. In this way, all the substation equipment could be protected with one arrester, however if substation is big, wave profiles along the substation up to entrance lines will not be totally protected and one set of surge arresters at each line entrance will be necessary.

There is a simplified formula, which provides an estimated valued of the zone protected by one surge arrester, which provides the length of the arrester connection. But EMTP Electromagnetic Transient Program or ATP Program should do the proper calculation.

On the other hand, the main characteristics of Surge Arresters are the Maximum Continuos Operating Voltage and the Maximum Residual Voltage for Impulse Wave & Switching Surge. These last values are for Insulation Coordination purpose. But one important characteristic is Line Discharge Class, which depends of the length of transmission lines connected to the substation. IEC standard indicates five types (1 to 5). This characteristic should be specified because indicates the energy dissipation capability of the arrester.