CPRI’S contribution to 1200 kV UHVAC equipment

On Mar 28, 2013

Fig: 1 View of corona cage for
study of corona performance
of bundled conductors.

Evaluation and consultancy
Abstract:
Ultra High Voltage (UHV) Research Laboratory is the specialized unit of CPRI located at Hyderabad. In the last three years, UHV RL, Hyderabad has tested many 765 kV, 1200 kV line and sub-station equipment including 800 kV DC line insulators as per International Standards. A brief description about the UHV equipment tested at UHV RL, Hyderabad is presented in the paper.

Introduction:
CPRI plays a significant role in supporting and developing country’s power sector. With its state-of-the art infrastructure and expertise, CPRI has made significant strides to the power sector in the country for testing of power equipment, improved planning, operation and control of power systems. Besides in-house R & D, CPRI also undertakes sponsored research projects from manufacturers and other agencies in different areas. To keep pace with the rapid development and growing demand of power, country needs the transmission of power at higher voltage levels. Thus, India is ushering in a new era of transmission at UHV levels. To meet the long term power transfer requirement and gain operational experience, PGCIL has established 1200 kV UHV AC test station in Bina (MP) under unique Public Partnership (PPP) model. CPRI is a member of the steering committee for PGCIL’s prestigious project of development of 1200 kV National Test Station. CPRI’s UHV Research Laboratory at Hyderabad has successfully completed consultancy work with respect to 1200 kV UHV AC system and tested many 1200 kV line and sub-station equipment which are in operation at 1200 kV National Test Station, Bina.

Fig: 2 Total set up showing
bundle conductor along with
insulator string and tower
window simulation for study
of air insulation.

CPRI’s contribution:
I. Consultancy works

1) Study of corona performance of octagonal conductor bundle in a corona cage:
The sub-conductor spacing for 1200 kV octagonal bundle conductor was optimized based on the corona performance in a corona cage.

2) Air insulation studies for 1200 kV UHV AC Transmission line:
A study on optimization of conductor to tower air insulation clearances for adoption in 1200 kV AC transmission lines using 8 BERSIMIS conductor bundle was successfully conducted.

3) Voltage distribution studies on 1200 kV Single ‘V’ Insulator string:
Optimization of grading ring size was successfully completed on 1200 kV single ‘V’ string consisting of 46 nos. of 420 kN disc insulators with nine different grading rings by measuring voltage distribution across insulator discs.

II. Evaluation of equipment
UHV Research Laboratory had made it possible for testing of equipment like Capacitor Voltage Transformers (CVTs), Current Transformers (CTs), Substation post insulators, String insulators, long rod porcelain and polymeric insulators, surge arresters and housings.

1) Evaluation of 1200 kV UHV Instrument transformers:
Dielectric tests on instrument transformers (CTs and CVTs) of rating 1200 kV were conducted. The insulation levels for 1200 kV equipment were indicated by PGCIL i.e. 2400 kVp lightning impulse, 1800 kVp switching impulse and 1200 kV rms short duration power frequency voltage. The test procedure was in general accordance with IEC: 60044-1 for 1200 kV CTs and IEC: 60044-5 for 1200 kV CVTs. Capacitance and dissipation factor measurement, Lightning impulse test, Chopped Lightning impulse test, switching impulse test under wet conditions, EMC Radio interference voltage test, short duration power frequency voltage test and Ferro-resonance & short-circuit withstand capability test (on CVTs) were conducted on instrument transformers.


Fig: 3 1200 kV CVT under test for radio interference.	Fig: 4 1200 kV long rod Polymeric insulator in PF test bay.	Fig: 5 1250 kV Lightning Arrester Housing in Impulse Test bay.

2) Evaluation of 1200 kV UHV Insulators:
Many 1200 kV line insulator strings and polymeric long rod insulators and substation insulators like 1200 kV bus post insulators were evaluated for their dielectric performance as per IEC: 60383 and IEC: 60168. 50 % lightning impulse flashover voltage test, switching impulse voltage test under wet conditions, RIV test, corona inception and extinction voltage test and short duration power-frequency voltage tests under dry and wet conditions are successfully conducted.

3) Evaluation of 1200 kV UHV Lightning Arrester and Lightning Arrester housings:
UHV RL successfully conducted dielectric tests viz. Lightning impulse voltage test, switching impulse voltage test under wet conditions and short duration power-frequency voltage tests under wet conditions on 1250 kV, 20 kA lightning arrester housing. Radio interference voltage test was conducted on 1250 kV Lightning Arrester.

Conclusion:
This paper had briefly discussed the general contribution of CPRI, Hyderabad in the area of 1200 kV AC.