EN 60984-1992 pdf download.Sleeves of insulating material for live working.
a) Clearance is the shortest electrical path from electrode to electrode around the open edge of the sleeve. Permissible tolerance is ± 25 mm.
b) In those cases where atmospheric conditions make the specified clearances impractical, the clearance may be increased by a maximum of 50 mm.
6.4.2 Electrodes
Four methods of mounting sleeves are provided, with the mounting positions and electrodes employed as described as follows.
NOTE Water electrodes should be free of air bubbles and air pockets. particularly in contact with the sleeves. Other electrodes should fit sleeves as snugly as possible and without distortion. Areas not in contact with the electrodes should he dry.
6.4.2.1 Water electrodes, inverted mounting
The small end of the sleeve shall be inverted and pulled through to the large end to form an annular trough as shown in cross section in Figure 7. The sleeve shall be immersed in water and the trough filled with water until the levels both inside and outside the trough are the same. This mounting shall not he used above 20 kV a.c. or 30 kV d.c.
NOTE Partkular care should he taken to avoid any sharp folds in the sleeve. which may cause premature dielectric breakdown at these points.
6.4.2.2 Water electrodes, sling mounted
A roll or rod of non-conductive material having a specific gravity heavier than water and a diameter larger or equal to 40 mm shall be placed across the sleeve at about the midpoint between the cuff and underarm edge. The sleeve shall be immersed in water with the roll in place and filled with water until the water levels are the same both inside and outside the sleeve, and the cuff and underarm edges are equidistant above the water line as shown in Figure 8.
6.4.2.3 Water electrodes, straight mounting
A layer of dielectric liquid having a high dielectric strength, with a specific gravity greater than 1.0 and insoluble in water, shall be placed in the test tank to a depth of approximately 100 mm. The tank shall then be filled with water to the desired level. The sleeve shall be immersed with the small end first, into the water until the cuff end is approximately 50 mm below the interface between the two liquids, as shown in Figure 9. The dielectric liquid separates and insulates the inside water electrode from the outside water electrode. This mounting may be used for all voltages, both ac. and d.c., although it may he necessary to increase the immersion depth in the dielectric liquid at the higher voltages.
The electrodes shall consist of two electrically conductive plates or shapes, constructed to conform closely to the inside and outside of the sleeve. Any edges on these shapes shall be so rounded as to eliminate sharp nicks and protuberances. The sleeve shall be drawn snugly and without stretching over the inner electrode and the outer electrode placed around it and adjusted to a snug fit as shown in Figure 10. For versatility in testing sleeves of different sizes the electrodes can be longer than those indicated, in which case masking of the edges with non-conductive material will permit the testing of shorter sleeves.
NOTE Because of potential ozone generation, this mounting is not recommended for a.c. testing of non•ozone resistant sleeves,
6.4.3 Test equipment
The test equipment shall be capable of supplying an essentially stepless and continuously variable voltage to the test piece. Motor-driven regulating equipment is convenient and tends to provide uniform
rate-of-rise to the test voltage. The test apparatus should be protected by an automatic circuit-breaking device designed to open promptly at the current produced by failure of a test piece under test. This
circuit-breaking device should be designed to protect the test equipment under any conditions of short circuit.
NOTE It is recommended that the test equipment system he inspected and calibrated at least annually.
6.4.4 Failure indicators
Sleeve failure indicators or accessory circuits shall be designed to give positive indication of failure.
6.4.5 A.C. voltage dielectric test
6.4.5.1 Test equipment
The desired a.c. test voltage can he most readily obtained from a step-up transformer energized from a variable low-voltage source. The transformer and its control equipment shall be of such size and design
that, with the test piece in the circuit, the crest factor of the test voltage (ratio of maximum to mean r.m.s. voltage) shall not differ by more than 5 % from that of the sinusoidal wave over the upper half of the range of test voltage.
Voltage control may be secured in one of several ways:
a) generator field regulation;
h) variable ratio auto-transformer;
c) induction regulator.EN 60984-1992 pdf download.