AlllOO ‘ITMOSS

IMBSIR 81-2192

Guide for Safe Operating

Procedures At High Voltage

Substations By NBS and Utility

Staff During the Field Calibration

of Coupling Capacitor Voltage

Transformers (CCVTs)

David L. Hillhouse

Electrosystems Division

Center for Electronics and

Electrical Engineering

U.S. Department of Commerce

National Bureau of Standards

Washington, DC 20234

100 ,S. DEPARTMENT OF COMMERCE

I U^U {{ 81-2192 ! 1981

I^lONAL BUREAU OF STANDARDS

national BUMAb

09 STAinuaBIS

laBSAST

APR 8 1981

NBSIR 81-2192 ^

GUIDE FOR SAFE OPERATING

PROCEDURES AT HIGH VOLTAGE

SUBSTATIONS BY NBS AND UTILITY

STAFF DURING THE FIELD CALIBRATION

OF COUPLING CAPACITOR VOLTAGE

TRANSFORMERS (CCVTs)

David L. Hillhouse

Electrosystems Division

Center for Electronics and

Electrical Engineering

U.S. Department of Commerce

National Bureau of Standards

Washington, DC 20234

February 1 981

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

GUIDE FOR SAFE OPERATING PROCEDURES

AT HIGH VOLTAGE SUBSTATIONS

BY NBS AND UTILITY STAFF

during the

Field Calibration of Coupling Capacitor

Voltage Transformers (CCVTs)

David L. Hillhouse

Applied Electrical Measurements Group

Electrosystems Division

Center for Electronics and Electrical Engineering

This guide contains a checklist of safe operating procedures

to be used by NBS staff in specific calibrations involving

high voltages ( a rbi tra ri 1 y , >600 V). Although these procedures

are believed to conform with relevant national standards and

codes, this guide is not to be construed as either a standard or

code. In addition, the contents do not represent the results

of NBS research. Use of this guide is restricted to the

purpose stated in the title. Publication, reproducti on , or

ope n-1 i terature listing is not authorized without specific

written permission from the Director, Center for Electronics

and Electrical Engineering, NBS, Washington, D.C. 20234.

November 1980
- 2

-

Guide for Safe Operating Procedures at High-Voltage Substations

by

MBS and Utility Staff

during

Field Calibration of Coupling Capacitor Voltage Trans fo rmers (CCVTs)

ABSTRACT

A guide for safe operating procedures during the field

calibration of CCVTs at high-voltage substations is presented

in eight major steps, as follows: (1) Offload and Set up; (2)

P re-cal i brate System Using Truck-Mounted Resonant Power Supply;

(3) Connect Standard Divider to High-Voltage Bus; (4) Calibrate

CCVTs; (5) Disconnect the Standard Divider from the High-Voltage

Bus; (5) Calibrate CCVTs on Next Phase; (7) Recalibrate Standard

Divider using Truck-Mounted Resonant Power Supply and; (8)

Dismantle Divider and Reload on Truck. Scope and general

considerations, including MBS staff responsibilities, are also

di scussed.
-3-

SCOPE

This guide documents certain minimum operating procedures

for carrying out safe calibrations in high-voltage substations'^.

It is presented in the form of a checklist designed to ensure

a systematic approach to safe calibration. The guide intentionally

does not address specific, detailed measurement procedures

having no bearing on safety. The complete calibration procedure

for CCVTs is described in references 1 and 2 (see footnote B bel ow ) .

In using this guide, it must be recognized that no procedure, no matter how carefully followed, can by itself

assure safe operation. In other words, there is no substitute

for experience and the development of safe work methods and

habits. Each substation is to some extent unique in the

specific hazards it presents; so that this guide is to be

regarded as one tool for promoting safe operation.

Since this guide does not constitute a description of any

research carried out by MBS and has been prepared primarily for

use by MBS staff, it is not available for general distribution.

However, interested parties, particularly clients of MBS

high-voltage calibrations, may request copies from the Electrosystems

Division, Building 220, Room, B166, National Bureau of Standards,

Washington, D.C. 20234.

A. High voltage is arbitrarily defined per the National

Electrical Code, Article 710, as >600 V.

B . Refe rences

1. "A Prototype Field Calibration System for Coupling

Capacitor Voltage Transformers (CCVTs)," D. L. Hiilhouse,

0. Petersons, and W. C. Sze, EPRI Report No. EL-690,

April 1978.

2. "A Prototype System for On-Site Calibration of Coupling

Capacitor Voltage Transformers (CCVTs)," D. L. Hiilhouse,

0. Petersons, and W. C. Sze, IEEE Transactions on Power

Apparatus and Systems, Vol . PAS-98, No. 3, May/June 1979.
- 4 -

G.ENERAL CONSIDERATIONS

The specific steps and precautions outlined herein are

to be supplemented and reinforced by continuous mutual

observation and warning of potential danger between and among

NBS and utility personnel. Some utilities assign a single

person to be responsible for safety alone.

In addition, this is a FAIR-WEATHER SYSTEM. It should

not be operated in rain, or if rain (especially th un de rs to rms

)

is known to be near the substation.

NBS staff in the field consists of a project engineer, a second professional*, and a senior technician experienced** in

high-voltage measurements. The project engineer has overall

responsibility for execution of the NBS portion of the

calibration procedure, including the detailed steps of this

guide. The engineer is also responsible for liaison and

coordination with utility personnel regarding all aspects of

safety. In addition, the engineer functions where appropriate

as an active crew member in the actual performance of detailed

safety steps, and may carry out or assist in carrying out

any of those procedures for which NBS is responsible.

The technician carries out, in conjunction and in

coordination with the project engineer and/or utility personnel,

the detailed steps of this guide. The technician is encouraged

to suggest modifications of these procedures in the interest

of improved safety, but may not bypass safety steps without

on-the-spot approval. If the technician oerceives what said

technician believes to be an unsafe practice occurring (or

about to occur), the technician shall without prejudice take

immediate correcti ve action no matter where the offender

stands in the normal chain of command.

*Exceptions - one qualified technician, who must be thoroughly

experienced in operating the system, may offload and set up

the system before the project engineer arrives (section 1),

and with the assistance of utility personnel deemed by the

technician to be qualified, run an abbreviated precal i b rati on

(section 2) to ascertain that the system is functioning properly

this will normally occur only on long trips, where the truck is

on the road more than one day, so that the professional staff travels

to the site only after the truck has arrived).

**The training consists primarily of "apprenticeship" to

experienced high-voltage personnel. In addition, safety

procedures such as this guide are issued, periodically updated,

and periodically reviewed with participating staff (especially

immediately before a field calibration trip). Personnel are

also encouraged to take CPR (cardio-pulmonary resuscitation)

and first aid courses, plus periodic refreshers.
-5-

PROCEDURE

1 . Offload and Set up

At a pre-calibration site inside the substation but well

away from energized high-voltage buses, the modular standard

divider is off-loaded and set up, using a truck crane operated

by a utility crew.

2 . P re-cal i brate System Using Truck-Mounted Resonant Power Supply

2.1 Short out the standard divider (against "static" pickup).

2.2 Connect heavy grounding cables from:

2.2.1 Standard divider to substation ground;

2.2.2 Truck to substation ground.

2.3 Enclose standard divider with portable bright yellow and

black safety fence sections.

2.4 Place safety-orange flags on safety fence corners.

2.5 Place battery-powered flashing red lights on safety

fence perimeter.

2.6 Place "DANGER - HIGH VOLTAGE" signs on standard divider

base.

2.7 Connect an external grounding lead, attached to truck

ground, to the standard divider's high-voltage lead

before that lead is connected to the truck's high-voltage

b u s h i n g .

2.7.1 A similar lead inside the truck's high-voltage

power compartment grounds the system's highvoltage resonant power supply.

2.8 Place rubber mats on the ground where personnel normally

step on and off the truck, and where they kneel to connect

signal cables from the test piece and standard divider.

2.9 Plug the 60-Hz, single-phase power cable (208 - 276 V,

depending on the substation) into the truck input panel.

UTILITY PERSONNEL will first have connected the oower

cable into their source. In a three-wire system, NBS

personnel must make certain the proper wire is grounded

at the source. Also, this power cable should never pass

beneath the high-voltage buses (large transient voltages

can be induced in the power cable during switching or a fault) .
- 6 -

2.10 Apply the truck's high voltage to the standard divider to

perform the pre-cal i b rati on , as follows:

2.10.1 Have £t least two people present and in close

communi cation:

2.10.1.1 Operator (on board truck);

2.10.1.2 Data taker and observer (outside truck).

2.10.2 Operator removes internal grounding lead from

resonant power supply.

2.10.3 Outside worker removes the outside grounding lead

from the divider before each operation, and replaces it afterward, but does so ^nly after

2.10.3.1 Receiving and acknowledging verbal

"voltage-off" assurance from inside

worker (operator) and receiving

operator's clearance to do so.

2.10.3.2 Observing the "power-off" green

light on the power supply control

consol e

2.10.4 Operator not only monitors the outside worker's

performance of the above, but also

2.10.4.1 Is constantly aware of the outside

worker's whereabouts.

2.10.4.2 Turns voltage on only when the outside

worker is in view and has assured the

inside worker that the grounding

lead is off and the area is clear.

2.10.5 Both operator and outside worker (but especially

the outside worker) make sure the area is clear

and warn any nearby people that the system is

"hot" before applying power.

NOTE: The following interlocks and safety features protect onboa rd personnel

a. - An interlocked door isolates the operator from the

truck's high-voltage power compartment. Power cannot

be applied unless this door is closed, and shuts off

if this door is opened.

b. The high-voltage power supply contol console has the

following safety features:
-7-

1. If the high voltage is shut down for any reason,

the power supply cannot be re-energized until the

voltage control is returned to zero.

2. High voltage arc-over is automatically detected, the

system is shut down, and an arc-over warning light is

lit. A further measure of safety against

high current and prolonged high voltage is provided

by the immediate de-tuning of the resonant power

supply by any substantial load change.

3

Connect Standard Divider to High-Voltage Bus

3.1

Move standard divider under high-voltage bus:

3.1.1 Making sure the standard divider top remains

grounded, disconnect the divider lead from

the truck (see also 2.7).

3.1.2 Place standard divider low-side grounding switch

in the GROUND position.

3.1.3 Place standard divider low-side output switch

in the OPEN position, and the range switch in

the appropriate position for the first calibration.

3.1.4 Disconnect signal cables and 60 Hz power cable

from the truck and

3. 1.4.1 Place their open ends on the rubber

mats (item 2.8), or other insulating

surfaces

3. 1.4. 2 Make sure these cables do not cross each

other or a grounding lead. DANGER: Do

not touch or remain within one or two feet

of these cables during high voltage switching.

3.1.5 Establish and maintain continuous contact with

utility personnel who are to perform the highvoltage switching, either by sight and voice or

by two-way voice radio (walkie-talkies).

3.1.6 From this time until the line has been deenergized (see 3.1.8, below) all personnel must

3. 1.6.1 Remain totally clear of the truck, or

remain totally on the truck. NEVER,

for example, should the feet be on the

ground and the hands on the truck, because

a switching surge can result in very

large potential differences between

"grounded" objects. It is in fact good

practice to remain totally clear or totally
- 8 -

on the truck at ALL times. A line

fault somewhere could cause unexpected

sw i tc h i ng . 3.1.7 Give the utility crew specific clearance to

de-energize the high-voltage bus. NOTE: This

is of course relative only to MBS readiness.

Actual clearance is given by utility operating

personnel, often in a control center many miles

away

3.1.8 UTILITY CREW WILL de-energize high-voltage bus.

3. 1.8.1 Open circuit breakers.

3. 1.8. 2 Open motor-driven bus disconnecting

switches ("disconnects").

3. 1.8. 3 Close hand-cranked bus grounding switches,

lock closed.

3.1.9 UTILITY CREW remove heavy substation grounding

cable from divider.

3.1.10 UTILITY CREW move standard divider under highvoltage bus.

3.2

Connect divider to bus:

3.2.1 Reconnect heavy grounding cable from standard

divider base to substation ground

CAUTION: double check this .

3.2.2 Set up safety fence, etc., around divider once

more, i.e., repeat steps 2.3 through 2.6.

3.2.3 UTILITY CREW will bolt divider high-voltage

lead to bus.

3.2.4 Make sure the divider low -side grounding switch

(see 3.1.2) is still in GROUND position, and the

output switch (see 3.1.3) is still in the

OPEN position.

3.2.5 Re-ascertain continuous contact with utility

switching personnel (see 3.1.5).

3.2.6 Make certain all personnel are

3. 2. 6.1 Totally clear of truck, or (see

3.1.6

and CAUTION)

3. 2. 6. 2 Totally on the truck, AND
-9-

3. 2. 6.

3

At least 100 feet (30 meters) from the

standard divider (there is a remote

but real chance of module rupture

during switching).

3.2.7 Give clearance for re-energizing the bus

(see MOTE with 3.1.7).

3.2.8 UTILITY CREW will re-energize the high-voltage

bus

.

3.2.8. 1 Unlock and open hand-cranked bus grounding

switches, lock open.

3. 2. 8. 2 Close motor-driven disconnects.

4 . Calibrate CCVTs

4.1 Reconnect power and signal cables to calibration

truck.

4.2 From behind the safety fence, and using electrical

gloves and regulation insulated "hot stick" for the

bus voltage involved (e.g., 230, 345, 500 kV) UTILITY

CREW will

4.2.1 Place divider low-side grounding switch in

OPERATE position.

4.2.2 Place low-side output switch in RATIO position,

and ascertain that the range switch is still in

the appropriate position.

4.3 At the option of the utility: close off an even larger

area around the divider with safety rope or tape, as a further precaution against casual intruders.

4.4 Connect test piece low side to calibrate system (UTILITY

CREW), proceed with calibration.

4.5 If divider range change is required during calibration,

UTILITY CREW, equipped and proceeding as in 4.2 above,

will place the RANGE switch in the new position.

5 . Disconnect the Standard Divider from the High-Voltage Bus

5.1

UTILITY CREW, once again equipped as in 4.2, above, will

5.1.1 Place standard divider low-side output switch

in the OPEN position.

5.1.2 Place standard divider low-side grounding switch

i n GROUND position.
- 10 - 5.2

MBS and UTILITY CREW now repeat steps 3.1.4 through

3.1.8 for de-energizing the high-voltage bus.

CAUTION: continue to emphasize especially 3.1.5

through 3.1.7. If at this po i nt the CCVT s on all

three phases have been calibrated, proceed to section

7 . If not;

6 . Calibrate CCVTs on Next Phase

6.1 UTILITY CREW will disconnect divider from bus, and

ground its top.

6.2 Move divider to next phase (UTILITY CREW - see also

3.1.9 and 3.1.10).

6.3 Repeat procedure outlined in 3.2.

6.4 Repeat sections 4 and 5 above.

7 . Recalibrate Standard Divider using Truck-M oun

t

ed Resonant

Power Supply

7.1 Move the standard divider back to its " pre-cal i b rate

location (UTILITY CREW).

7.2 Repeat section 2, a 1

1

steps.

8

.

Dismantle Divider and Reload on Truck

8.1 Follow the procedures and precautions outlined in

section 1

.
NBS-n4A (REV. 2-8C) U.S. DEPT. OF COMM.

4.

BIBLIOGRAPHIC DATA

SHEET fSee instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR 81-2192

2. Performing Organ, Report No. 3.

TITLE AND SUBTITLE

Publication Date

February 1981

Guide for Safe Operating Procedures at High Voltage Substations

by NBS and Utility Staff

5. AUTHOR(S)

D. L. Hillhouse

6. PERFORMING ORGANIZATION (If joint or other than NbS, see in struction s) 7. Contract/Grant No. national bureau of standards

DEPARTMENT OF COMMERCE 8. Type of Report & Period Covered

WASHINGTON, D.C. 20234

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City, State. ZIP)

Same as no. 6

10. SUPPLEMENTARY NOTES

I I Document describes a computer program; SF-185, FlPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most significant in formation. If document includes a significant

bi bliography or literature survey, mention it here)

This summary documents minimum procedures and operations necessary to provide

for a safe calibration in a high voltage substation. The summary is in the

form of a checklist so that it outlines a formal, systematic approach to safe

cal i brat ions.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s) Calibration; coupling capacitors; high voltage measurements; safety; substations;

voltage transformers.

13. AVAILABILITY

1 1 Uni imited

ly 1 For Official Distribution. Do Not Release to NTIS

[*n Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

[231 Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO, OF

PRINTED PAGES

15. Price

USCOMM-OC 6043-P80
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