ECN Forum Forums Code Related Discussion NEC & other Code issues 250.30

The 1999 NEC 230.30(a)(4) text, which I believe would have covered the Xo being grounded and not a conductor extended to the system disconnect, by noting on a violation " 1999 NEC 250.24(b)", but the 2002 NEC did not retain those words.

Also have not seen the existing 4160V source for this Plant. Believe plant is about 25 years old.

At present time, do not know if the 4160V is delta or wye.

If a delta 4160V system, is an EGC required (in same raceway) with each feeder along with the individual 5KV drain ( sheild ) of each Phase cable? Appears 250.4(B)would require all equipment to be so bonded.

As can be seen by the questions, have not had many HV in plant systems.

[This message has been edited by Gwz (edited 12-13-2002).]

The “drain” wires are not there for equipment bonding. They are not sized for that. There purpose is summarizes below from the okonite web site. An EGC must be installed.

Functions of Shielding

A strand shield is employed to preclude excessive voltage stress on voids between conductor and insulation. To be effective, it must adhere to or remain in intimate contact with the insulation under all conditions.

An insulation shield has a number of functions:
(a) To confine the electric field within the cable.
(b) To obtain symmetrical radial distribution of voltage stress within the dielectric, thereby minimizing the possibility of surface discharges by precluding excessive tangential and longitudinal stresses.
(c) To protect cable connected to overhead lines or otherwise subject to induced potentials.
(d) To limit radio interference.
(e) To reduce the hazard of shock. If not grounded, the hazard of shock may be increased.