High Voltage Phasing Sticks for Substation Switching

Why Paralleling Demands Verification

Closing a tie breaker or paralleling two substation feeders that are out-of-phase produces a fault current limited only by source impedance. The resulting magnetic, mechanical, and thermal stresses can damage transformers, conductors, and breakers. Even a 30-degree phase angle difference creates current spikes that trip protection. Phasing sticks verify that two energized busses are in phase—and identical in rotation—before the operator closes the breaker.

Voltage Class and Selection

Phasing sticks are rated by maximum line-to-line voltage (typically 5, 15, 25, 35, or 69 kV) and must include a fiberglass shaft of the appropriate length to maintain minimum approach distance per OSHA 1910.269 or IEEE 516. Always select a stick rated above your system voltage, and verify the stick has a current calibration sticker (annual electrical testing required).

How a Phasing Stick Works

The two-stick pair contains a high-impedance voltmeter that reads the voltage between the two probe tips. When connected to in-phase conductors of equal voltage, reading is near zero. Out-of-phase, the reading approaches twice line voltage. Modern digital phasing sticks display both voltage and phase angle on a wireless transmitter to a remote display, removing the operator from the live work zone.

Field Procedure

1. Prove the sticks on a known-good live source—read phase to ground, expect rated voltage
2. Self-check: probe the same conductor with both tips, expect zero
3. Touch one stick to bus A and the other to bus B
4. Read voltage and angle. Zero volts = in phase, ready to parallel
5. Re-prove the sticks after the test (live-dead-live confirmation)

Common Failures

• Failed annual hi-pot test makes the stick unsafe; never use without current sticker
• Wet or contaminated fiberglass shaft reduces dielectric strength dramatically
• Battery failure in digital models leaves stick reading zero falsely

EK Phasing Equipment

EK phasing sticks cover 5–69 kV with wireless display options and integrated sequence detection. All units ship with annual hi-pot certificates and a calibration logbook compatible with utility audit programs.