What Is a High Voltage Phase Detector?
A high voltage phase detector is a device used to check whether the phase rotation of a high-voltage (600 VAC or higher) power line is a reverse phase, or normal phase.
It is mainly used in high-voltage power systems and plays an important role in ensuring the safety of the power supply. In power systems, three-phase AC power (usually 50 or 60 Hz) is often used. a device that detects which of the three phases of a three-phase power supply is arriving in which order and verifies that the phases are connected in the correct sequence.
The overall length of a high-voltage detector is long enough to allow a separation distance of 30 cm or more.
They are often used mainly for cable systems, and are shaped like two-phase detectors connected together so that two cables can be tested. While most low-voltage phase detectors check phase rotation by inserting three phases simultaneously, High Voltage Phase Detectors are designed to check phase rotation of two phases for convenience.
Applications of High Voltage Phase Detectors
High voltage phase detectors are used in power supply and construction work.
1. Power Supply
This device is used to ensure the safety of power supply by detecting the correct phase sequence and connection in the power system. If there is an incorrect phase sequence or missing phases, the phase analyzer will issue a warning and detect the problem early.
High voltage systems often have transformers and electric motors connected to the secondary side. If the phase rotation is reversed, all connected electric motors will rotate in reverse.
Such an accident may cause failure of pumps, fans, etc., which are the load of the electric motors. Industrial rotating equipment is often expensive and can cause significant losses. If a reverse phase is found, it is important to carry out reconnection with the wiring.
2. Construction Work
In construction work, it is used in the installation of new equipment. High voltage phase detectors can be used to confirm that the phase rotation is as designed.
Principle of High Voltage Phase Detectors
A 3-phase AC power supply is input to the high voltage phase detector. This is usually from the power system or a generator. The three incoming phases are detected, and each phase is monitored via a dedicated sensor or circuit.
The three detected phases are compared. If the phases are connected in the correct phase sequence, the phase period or phase difference is constant. The results are often visualized through a display panel or indicator.
If the phases are connected in the correct phase sequence, the lamps and indicators on the display panel light up. If the phase sequence is reversed or a phase is missing, a warning or alarm is issued to alert you to the problem.
Types of High Voltage Phase Detectors
Phase detectors are broadly classified into two types: contact phase detectors and non-contact phase detectors. The non-contact type is the most common type of high voltage phase detector.
1. Contact Type
A contact high voltage phase detector is a device that detects the phase state by physically contacting the power supply circuit; it is directly connected to the un-insulated portions of the three phases to measure the power supply voltage and directly check the phase rotation based on the phase difference.
This method is often used in low-voltage three-phase circuits of 200V or 400V. When applied to high-voltage systems, the low-voltage portion is measured via an instrument transformer. Since an accidental ground fault or short-circuit of high-voltage power can cause a powerful spark that is extremely dangerous, products that directly contact the high-voltage terminals are not often sold.
2. Non-Contact Type
A non-contact high voltage phase detector is a device that detects the phase state without physical contact. Currently, non-contact phase detectors are the mainstream for both low and high voltage, and most high voltage products are non-contact.
The principle is based on electrostatic induction. The inside of the phase analyzer has a high resistance and is grounded to earth through a human body to form a closed circuit. The voltage induced from the power line is detected in the closed circuit, and the phase difference between the induced voltages of the two phases is detected.
A low-voltage phase analyzer generally consists of three clamps, so that the phase rotation of the three phases can be checked. High voltage phase detector, however, require a greater separation distance and are often constructed to detect the phase difference between two phases due to the larger size of the phase detector body.