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Washing of insulation under operating voltage

Washing of tainted insulation of overhead power lines and 35-500 kV substations

Long-standing practice of using different methods of preventing overlapping of insulation with contaminants on ВЛ and ОРУ led to the conclusion that the use of low-pressure jets of water as a tool to remove dirt from the insulators has significant advantages. First of all, it is an opportunity to clean up the insulation under voltage (without turning off electrical equipment), high performance (speed cleaning), ease of use and simplicity of technical resources, smaller material and financial expenses comparing with other ways of preventing overlapping of insulation with contaminants.

Basing on the experiences of domestic work on washing of the insulation under the operating voltage and according to the relevant regulations and specific use of modern high-voltage equipment, SPA "TECHNOSERVICE - Electro" and JSC "UES FGC" have developed the "INSTRUCTIONS for washing of polluted insulation, overhead transmission lines and substations 35 ÷ 500 kW with continuous low-pressure streams of water. "

The main element of tooling for these works are the special tubs, which allow to create a compact low-pressure jet of water (up to 10Atm) which lets washing the insulation of overhead lines and switchgears from 35 kV to 500 kV.

Specialists of CJSC SPA "TECHNOSERVICE - Electro" have designed the tub FLOW-1F, which due to the original design and application of advanced materials has far exceeded earlier counterparts for all major specifications.

FLOW-1F washing tub

Mobile washing installation kit is made up of two special purpose vehicles, mass-produced by industry. The base car is a cistern. The second is a special telescopic tower, which is used when lifting the operator to wash the insulators.

A cistern can be mounted on any chassis, preferably off-road. Tank capacity should be 4 - 5 m3 of water. A cistern can be of a larger capacity; however, the maneuverability of the vehicle should be taken into account, as in work at the substations that quality is essential. Cistern must be equipped with a centrifugal pump with performance of 1200l/min and flow at 100 meters. The pump is driven by the vehicle engine via transmission gearbox.

Maximum height the basket of telescopic tower must be is at least 15 meters. The use of hydraulic lifts of other configurations in which a basket with a man has the ability to move in the horizontal plane is not allowed.

Mobile washing installation includes the following devices, instruments and equipment:

1. Special tubs - 2 sets.

2. Bevel-cylindrical jets with the outlet diameter d0 = 7, 8, 9, 10 and 12 mm - 2 sets.

Use of a set of jets with different outlet diameters helps to save water.

3. Rubber sleeves (hoses), 15 m long - 4 pcs.

Inner diameter of 38 mm is designed for water flow of 160 m. Each tube at both ends is reinforced with a special "Bogdanov" coupling nut

4. Grounding wires (copper, stranded, flexible, in the shell), section - 25 mm2, 15 m long - 4 pcs.

Two wires are reinforced with clamps at one end, tipped for M5 bolt at the other.

5. A device for measuring the speed and the direction of wind - 1 pc.

6. Device for determining the electrical conductivity of water (conductivity meter) – 1 pc


When washing the insulation it is required to consider the following factors:

Wind speed and direction;

Place of installation of special equipment;

Place of installation of temporary protective grounding

Volume resistivity of water.

When works on washing of insulation of power lines are made, for each foot should be drawn up a chart of washing flow, in which the following should be reflected:

1. Type of foot;
2. Options for approach of machinery;
3. Options for placement of special equipment with the prevailing wind patterns

   

Sample of routing for washing with the location of telescopic tower and cistern at anchor steel foot of 500kV line, the height of lifting the basket and insulator washing sequence in accordance to the wind direction.

Washing of insulation in a field at the anchor steel foot of 500kV line using telescopic tower.

Washing of insulation in a field at the anchor steel foot of 500kV line from the ground - the barrel-breaker is mounted on a tub carriage.

At ОРУ when washing the insulation, one of the main conditions is the correct placement of the operators in accordance to the wind rose reflected in the process chart.

 

Position of operators and sequence of washing the insulators of 500 kV breaker

Symbols:

1. - The position of the 1st operator.

2. - The position of the 2nd operator.

The numbers show the sequence of washing the insulators in accordance to the direction of wind

To control and calculate the necessary supplies of water during washing, the calculated curves are useful.

These curves are required to calculate the total volumes of water used to wash the insulation of the foots of overhead lines, the entire overhead, for 1 cell of ОРУ etc.

The figure shows the water flow curves as a function of pressure H, and the diameter of the outlet jet d0 [Q = f (H)]

These curves are based on points, which are calculated by the formula:

 m3/s.,

where H is head of water, m;

Ви is a characteristic of expiration Ви=2Ки, where 2 = 0.9;

Ки is a release coefficient = 12,106d04, where d0 is the diameter of the outlet jet, mm