Frankfurt (Germany), 6-9 June 2011 Ger Sebregts – Alliander - The Netherlands – Session 1 Network Components – 0037 Investigation towards the upgrading of existing 10 kV cables and accessories to an operation voltage of 20 kV

Frankfurt (Germany), 6-9 June 2011  Purpose of the project;  Programme;  Cable type and construction;  Accessory types;  Theoretical study;  Type test;  Long term test;  Decision model. Project Summary Investigation towards the upgrading of existing 10 kV cables and accessories to an operation voltage of 20 kV"

Frankfurt (Germany), 6-9 June 2011 Purpose of this project  Major reason to consider upgrading: standardization;  To try to approach the limits;  Prevent public inconvenience by replacing cable;  To indicate the risks for cable and accessories;  To demonstrate that the risks can be controlled.  Upgrading is risky, but also a challenge.

Frankfurt (Germany), 6-9 June 2011 Purpose for standardization

Frankfurt (Germany), 6-9 June 2011 Participants  Parties participating in this study are: Liander (grid-company); KEMA; Technical University Delft.

Frankfurt (Germany), 6-9 June 2011 Cable type and construction  6/10 kV cable;  Single Phase, 630 mm² Aluminium;  Longitudinal watertightness (#);  Copper screen;  PE outer sheath (#);  1300 ckm in operation. (#) Combination is supposed to be radial watertight.

Frankfurt (Germany), 6-9 June 2011 Type of joints  Heat shrink 10 and 20 kV;  Three manufacturers.

Frankfurt (Germany), 6-9 June 2011 Programme Step 1. Theoretical study; Step 2. Type testing; Step 3. Long term testing; Step 4. Decision model.

Frankfurt (Germany), 6-9 June Theoretical study a) Electrical ageing; b) Determine the value of exponent n; c) Possible other effects than electrical ageing; d) The position of the accessories; e) International orientation; f) Risk Analysis; g) Diagnostic selection method.

Frankfurt (Germany), 6-9 June b. The value of n (1)  Exponent n (power law) has been evaluated;  Values for n between are reported;  The production of MV cable will be less sophisticated (newly producing countries);  For this project the value of n=9 has been chosen.

Frankfurt (Germany), 6-9 June b. The value of n (2) Long term test 5 months

Frankfurt (Germany), 6-9 June d. The position of the accessories  The accessories differ from the cable: They are “man made” in the field; Effective testing after installation is not always performed; Unfavourable failure behaviour  Consequently accessories have to be tested very seriously!

Frankfurt (Germany), 6-9 June e. International orientation  The following experiences are available on this subject: CIGRE WG B1-11 “upgrading of existing cable systems”; Work performed at University of Chemnitz together with utilities in Dresden and Chemnitz; Work performed in China ( University of Xi’an ).

Frankfurt (Germany), 6-9 June Type testing 20 kV requirements (1)  Performed on 10 kV cable & 10/20 kV accessories;  To determine (first step), the feasibility upgrading;  Only relevant tests (= Electrical tests);  If 10 kV accessories will not satisfy the requirements, they will be replaced by 20 kV accessories.

Frankfurt (Germany), 6-9 June Long term testing  Depending on the results of type test this long term test will be performed on 10 or 20 kV accessories;  10 kV kabel (with operational experience of several years) will be tested as follows: During 5 months; Increased voltage 1.7 Uo; Daily heat cycles; PD during the long term test.

Frankfurt (Germany), 6-9 June Decision model  Long term testing: Cable fails, - no upgrading; Accessoires 10 kV fails, - 10 kV cable with 20 kV accessories.

Frankfurt (Germany), 6-9 June 2011 Status of the programme Step 1. Theoretical study (finalized); Step 2. Type testing (finalized); Step 3. Long term testing (next month); Step 4. Decision model (december 2011).

Frankfurt (Germany), 6-9 June 2011 Thank you for your attention !! Upgrading of 10 kV XLPE cable to 20 kV