Medium / High-Voltage Phase Testers

Medium-voltage phase testers check phase coincidence and phase sequence before two lines or two supply sources are connected. Ring network switching, new line connections and commissioning after cable joints are the most frequent tasks. The measurement is made by bringing the units at the ends of two separate sticks into contact with the two conductors to be compared at the same time, so a two-person team is required.

The main difference between the two models in this subcategory is how the two units are linked: in the HPI-S20W the units are connected by a fibre-optic cable, while in the HPR the link is wireless.

Which model?

Model	Operating voltage	Typical use
HPI-S20W	AC 22 kV – 42 kV	Overhead lines; 6 m standard test distance, up to 30 m with optional cable
HPR	22 kV and 34.5 kV networks (confirmed in the quotation)	Wireless pair; phase test within 5 m, straight (HPR-S20) or universal-joint (HPR-U20) stick

The HPI-S20W detects same phase / 120° different phase and 120° forward / reverse phase sequence; its light indicator can be read at 8000 lux ambient light. Where two distant poles or disconnectors must be compared, the extendable optical link is the key advantage. The HPR offers voltage detection with one detector and phase and phase-sequence checking with two; it is more practical for crews who prefer not to carry cables on site.

Points to note in use

• A phase tester is not used to verify the absence of voltage; a hot-stick high-voltage detector of the appropriate class is required for that.
• Do not crush the optical cables or bend them sharply; make sure the sticks are clean, dry and undamaged.
• Both operators must hold the stick only by its grip area and use PPE suited to the MV class.

For the low-voltage option see phase testers; for step-by-step application see our article What Is a Phase Tester and How Is It Used?.

Frequently Asked Questions

Which model should be chosen for a 33–35 kV ring network?

33 kV and 35 kV lie within the AC 22 kV – 42 kV range of the HPI-S20W. The HPR is offered for 22 kV and 34.5 kV networks, so its suitability for your network is confirmed in the quotation. If the distance between measuring points exceeds 5 m, the HPI-S20W is the right choice; if a wireless, lightweight set is the priority, consider the HPR.