For grounding of the puncturing adaptation the special grounding conductor shipped in the soil on depth not less than 0,5 m or armor of a cable are used. The grounding conductor joins armor collars; the bronelenta under a collar has to be cleared.
for transformers on voltage of 110 kV and more — 16 h at relative humidity to 75% and 10 h at relative humidity to 85%. If time of survey of the transformer exceeds specified, but no more than v2 time, control subdrying of the transformer has to be carried out
After definition of a cable check of absence is made on is mute tension. According to PTB such check has to by the special adaptation providing a cable to veins and their grounding. Thus in wells and tunnels the adaptation has to have remote control.
Before opening of couplings or cutting of a cable it is necessary to make sure that these operations will be made on that cable on what it is necessary that this cable is disconnected and the technical actions necessary for the admission to works on it are executed.
In transformers to 630 kv-A with thermosiphon filters test of oil is not selected. At unsatisfactory characteristics of isolation works on isolation restoration, replacement of oil and silica gel in thermosiphon filters are performed
By complex consideration of results of measurements (resistance of isolation, tg , capacity of windings concerning the earth and each other, a relative gain of an at change of frequency or duration the category is given a preliminary estimate of a condition of isolation and the conclusion about need of drying of isolation. When commissioning the new transformer it is necessary to take into account conditions of transportation, storage, correctness of carrying out installation works, oil in a transformer tank, and also duration of finding of active part in the depressurized state at audit during installation (the same at repair.
By results of measurement determine conditions of a magnetic conductor of the transformer (short circuit of sheets of steel of a magnetic conductor, education by various reasons of short-circuited contours in fastening knots a magnetic conductor. Value of losses of XX in operation is not normalized as over time because of deterioration of properties of steel of loss of XX tend to increase. If the magnetic conductor has no defects, measurements show equality of losses on extreme cores (at new transformers distinction no more than 10%) and the value of losses increased approximately by 30% on an average core of a magnetic conductor.
Measurement of losses of idling for transformers of 10000 kVA and more is made at the lowered tension (excitement) before measurements of resistance to a direct current to avoid increase of losses of XX because of transformer steel magnetization. Removal of residual magnetization is made single smooth increase and the subsequent smooth decrease in excitement by an alternating voltage.
Tests and measurements of power transformers, are made with a certain frequency in use for check of the main technical characteristics of the transformer and its separate knots.
at the lowered tension losses of idling according to schemes according to which measurement at manufacturer was performed are measured. Frequency and value of the brought tension have to correspond to the factory
windings their removal from the core or not. The greatest test tension at partial repair is accepted equal 90% of tension accepted by plant. At capital repairs without replacement of windings and isolation or with isolation replacement, but without replacement of windings test tension is accepted equal 85% of factory test tension
It is made by the oil column pressure which height over the level of the filled dilator is accepted equal 0,6 m; for tanks wavy and with lamellar radiators — 0,3 M. Prodolzhitelnost tests not less than 3 h at a temperature of oil are not below 10 °C
Along with the general requirements of safety measures which are fulfilled during the works on cable lines, exist additional for the admission to works on the operating lines. Such admission is necessary for carrying out the following main operations: comprehensive shutdown of the line; grounding of the line; definition of the line on the route; a puncture of a cable and its grounding on place of production of works, cutting of a cable and at a opening of the coupling.