IEEE 1732-2017 pdf download

IEEE 1732-2017 pdf download.IEEE Recommended Practice for Space Charge Measurements on High- Voltage Direct-Current Extruded Cables for Rated Voltages up to 550 kV
4. Recommended space charge measurement methods
The space charge measurement methods recommended for space charge measurements on high-voltage direct-current (HVDC) extruded cables for rated voltages up to 550 kV are the following:
a) The pulsed electro-acoustic (PEA) method
b) The thermal step method (TSM) For details about the PEA method, reference shall be made to CIGRÉ Technical Brochure (TB) 288:2006. For more details about the usage of the PEA method in the case of cable geometry, see Annex A. For details about the TSM, reference shall be made to CIGRÉ TB 288:2006. For more details about the usage of the TSM in the case of cable geometry, see Annex B.
5. Space charge measurements during the prequalifcation test
5.1 Introduction Given the importance to space charge formation of cross-linking byproducts associated with the crosslinking agent dicumyl peroxide, and of anti-oxidants and molecular voltage stabilizers, and the efect of humidity (water) and the relatively rapid transmission of water through extruded insulation (in particular polyethylene and ethylene-propylene rubber), considerable care shall be exercised in performing PEA or TSM space charge measurements on HVDC extruded cables. Exposure to humid environments shall be minimized and limited strictly to the measurement duration. Constant and predefned values of cable conductor temperature, temperature gradient across insulation wall, and humidity of the surrounding environment shall be maintained during such measurements, to every extent possible. Ambient conditions during PEA or TSM measurements shall be recorded and included in the space charge measurement report.
5.2 Measurements by means of the PEA method
5.2.1 Measurement times During the long-duration voltage test of the prequalifcation (PQ) test (described in CIGRÉ TB 496:2012, page 14, 3.4) two sequences of space charge measurements by means of the PEA method shall be carried out at the following times:
a) Before starting the long-duration voltage test of the PQ test: This frst sequence of space charge measurements shall be carried out on a virgin (unaged) cable sample identical to the cable employed in the PQ test loop (see CIGRÉ TB 496:2012, subclauses 1.5.2, 3.3, and 3.4); this will serve as a reference for calibrating the PEA measurement set-up.
b) After the completion of the long-duration voltage test of the PQ test: This second sequence of space charge measurements shall be performed on an aged cable sample identical to the cable employed in the PQ test loop and subjected to the same long-duration voltage test as the PQ test loop.
5.2.2 Preparation of cable sample for space charge measurement with the PEA method For each sequence of space charge measurements with the PEA method at the times established in 5.2.1, the cable sample shall be arranged in a cable loop consisting at least of:
— A cable of length sufcient to perform the space charge measurements by means of the PEA method satisfactorily.
— Two terminations. Laboratory terminations are acceptable provided that they do not give rise to any fashover during both the space charge measurements and the whole PQ test.
The two sequences of space charge measurements with the PEA method at the times established in 5.2.1 shall not be performed on the same cable loop. Indeed, the PEA method requires that the outer shielding layer of the cable is removed and the outer semiconductive layer of the cable is exposed; this modifes the de-gassing rate and the efect of humidity on the cable loop subjected to space charge measurements compared to an unmeasured PQ test loop. The two diferent cable loops for the two sequences of space charge measurements at the times established in 5.2.1 shall be obtained according to one of the two following alternative procedures:
a) The two cable loops shall be both obtained from the PQ test loop—provided that its initial overall length is sufcient—as follows:
1) The frst sequence of space charge measurements with the PEA method at the frst time established in 5.2.1 shall be performed at a location of the PQ test loop where the PEA set-up can be properly installed.IEEE 1732 pdf download.IEEE 1732-2017 pdf download