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Feed Configuration Worksheet

Feed Configuration Worksheet | Talite Combined Substation Transformer

Feed Configuration Worksheet

Four questions that fix the high-voltage arrangement before the tank is designed. Getting these wrong after drawing approval means a new tank, not a change order.

Worksheet

1. How many sources can reach this location?

2. Does the cable route continue past this unit to another load?

3. Must an operator be able to isolate this unit without dropping the rest of the circuit?

4. Is a future second source planned within the asset life?

Configuration to specify Answer the four questions and the worksheet resolves here.

Bushing Count Reference

Bushings Arrangement Typical use Watch out for
Three Radial feed Single incoming circuit terminating at the unit No pass-through and no second source without changing the tank
Six, in two sets of three Loop feed, H1A–H3A and H1B–H3B Cable in on the A side, out on the B side Selection is a manual or automated switching action, not automatic transfer
Six, B side capped or arrester-fitted Loop-feed unit on a radial circuit Last unit in a chain, or a site awaiting a second source No redundancy benefit while the B side stays dead
Three plus rotatable feed-through inserts Extended radial Adding arresters or a second cable set Cannot select between an A side and a B side

Switch Selection

Device What it controls Combinations Choose it when
Three two-position loadbreak switches Coil, A side and B side independently More than four The operating philosophy needs isolation and transfer handled separately
One four-position loadbreak switch Combined source selection and sectionalising Exactly four The operating sequence is fixed and simplicity matters more than flexibility
Bayonet fuse with backup current-limiting fuse Isolation of this unit on a fault Always, on a multi-unit circuit

What the Transformer Cannot Supply

Whatever the worksheet returns, the hardware inside the tank does not deliver these. They belong to the network design and should appear in a different part of your specification.

  • A second source of supply
  • The open point and its location on the circuit
  • Automatic restoration after a feeder fault
  • The protection scheme and its coordination settings
  • Utility acceptance of the installed arrangement

Sources

  1. IEEE C57.12.34-2022, covering connector, bushing and terminal arrangements for radial or loop-feed systems. standards.ieee.org
  2. Maddox, Guide to Radial and Loop Feed Transformers. maddox.com