LA HOR E: A preliminary investigation into the recent tripping-based major power breal(downs in Punjab, Sindh and Balochistan suggests the `flashovers` occurred on lines due to reducedinsulationlevelsunderheavy fog conditions.

`There is a need to adopt live line maintenance practices so that the supply can be maintained according to the insulation levels to their design levels and without compromising system reliability (no outages for maintenance),` suggests the findings the National Transmission and Dispatch Company (NTDC) submitted to the Water and Power Ministry.

`Besides, revision of insulation design of transmission lines under new environmental conditions can also be considered.

The ministry was informed that for most part, 132kv transmission lines tripped in recent days, causing significant load loss to the system.

The malfunction led to over-voltage on 220kv and 500kv transmission lines. The protection system tripped these lines, either due tonashovers on insulator strings or simply to avoid equipment damage at terminal stations (substations).

According to the preliminary investigation, under dry conditions, most of 132 kv and 220 1(v system trippings could have been avoided.

According to the official record, on Dec 8, 10 132kV transmission lines by the distribution companies at Kala Shah Kaku (Badu Mali, Attabad, Ittehad Chemical, Shahdra, Shamkay, Narang and GhaziBatapur) tripped from 10:18pm to 11:12, leading to tripping of the four NTDCs 220kV lines (Kala Shah Kaku) at about 10:58pm and 11:15pm to 11:20pm.

Later, more 1321(V lines brolce down leading to tripping in more 220kV lines/grid stations from 11:23pm to 11:55pm. Similarly, several 132kV transmission lines tripped first on Dec 9 due to massive fog, leading tripping of the 220 and 500kV transmission system in parts of Punjab, Sindh and Balochistan.

A Lahore Electric Supply Company official said the Water and Power Ministry secretary had also sought explanation from distribution companies into the cause ofbreakdowns.

According to a senior NTDC official, fog and pollutants are a problem behind tripping of the lines.

`It is a not a matter of tripping of the 132kV lines or the 220kV first, as a mixture of worst pollution (dust particles) and the moisture caused by the fog continue to cover the lines, leaving a cascading effect on the system and leading to power outages, NTDC Managing Director Fayyaz A Chaudhry told journalists on Tuesday.

`The fog alone cannot deteriorate the system on such a huge scale, as the pollution caused by the increasing traffic, industry, dust and brick kilns is the main source of choking the system,` he said.

A maintenance system was in place but it was not practically possible to wash the thousands of kilometers long transmission lines manually, he explained.

`The only sustainable way to get rid of the problem is to devise a comprehensive plan to improve the environmental conditions,` he added.

`Side by side, a plan to increaseinsulationlevelofthe transmission lines is also being increased to avoid or minimise affects caused tripping of the lines due to pollution.