Insulation coordination is both an art and science. The aim of insulation coordination is to reduce the cost and disturbance caused by insulation failure to an economically and operationally accepted level. It essentially verifies the rating as well as location of lightning arresters in substation to realise the protective margin required.

KNR has an EMTP group equipped with EMTP software package and a well-documented library with IEEE, CIGRE and HV engineering books to handle insulation coordination studies for AIS and GIS substations up to 765kV. We have an impressive record of having carried out more than 50 such studies in 9 countries till date for substations and transmission lines. Our clientele includes most big names of the global electrical industry.

The group is led by PhD scholars in HV engineering ably assisted by a group of HV engineering post graduate professionals and EMTP analysts.

KNR is an approved consultant of DEWA for Insulation Coordination Study on exclusive basis besides being accepted by utilities of repute across the middle east and South East Asia.

Value Addition

Insulation coordination study determines the selection and verification of surge arrester at right place to limit various types of overvoltages in the system within the equipment withstand levels. Maximum overvoltage like Temporary overvoltage, switching overvoltages, lightning overvoltages and Very fast front overvoltages are determined for various operating conditions.

Protection of equipment from transient voltage beyond the capability of their typical insulation ratings through coordinated selection and placement of surge arresters.

Insulation Coordination Methodology

Step 1: Select most onerous path configuration of the system for the study.

Step 2: Collect, compile and validate data as per data questionnaire.

Step 3: Model the components of the system - Power Transformer, GIS section - OHL section, Surge arresters, cable, etc. & Develop network diagrams for the modelled system for EMTP analysis.

Step 4: Study the specific requirements with respect to operational philosophy and practice and select Lightning current stroke peak and shape for carrying out Lightning impulse overvoltage performance under shielding failure and BFO conditions.

Step 5: Decide the number of cases to be studied for Insulation Coordination exercise.

Step 6: Run EMTP-RV analysis with MicroTran version 3.25 to assess voltage stresses at surge impedance transition boundaries.

Step 7: If the nominal system voltage is above 300kV, carryout SOV studies for various conditions to validate the Insulation Coordination achieved based on LIOV performance.

Step 8: Study the Alternatives of the configuration satisfying Insulation Coordination protective ratios and choose the best.

Step 9: Construct the waveforms of the voltage stresses at surge impedance transition boundaries for the conditions studied.

Step 10: Study the controlling effect required and location to select type and characteristics of the surge arresters & specify the class and energy capacity required.

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