High Voltage Test Equipment

High Voltage

Experts in high voltage testing

Seward have been designing and manufacturing high voltage test equipment for over 37 years and continue to innovate and bring the best instruments to the market. Choose from phasing sticks, safe discharge rods, voltage indicators and more. Whatever your high voltage test requirements are, we have a solution for you.

The KD1E is a neon HV potential indicator suitable for use on earthed neutral systems up to 11kV.

A highly robust, portable AC/DC voltage indicator. This potential indicator provides a means of confirming the presence of voltage on earthed neutral electrical circuits. Conforming in design lengths to recommended, creepage and safety standards, the KD1E series features high grade PVC tubing and incorporates totally encapsulated resistor chains.

For additional safety a proving unit (PH3) is available and should be used before and after the high voltage indicator is employed.

Key Features Duplicate neon indicators within shock resistant sleeves. Permanently connected earth cable. Hand guards on both elements. Direct access possible to practically every type of vertical or horizontal metal clad switch gear. UK Electricity Council Approval list G9

What is High Voltage Testing?

Circuits and equipment are generally classified as ‘High Voltage’ when they have a nominal voltage exceeding 1000 Volts AC or 1500 Volts DC. High voltages are generally found in the electrical distribution network where it is common to see systems operating at 11,000 VAC, 33,000 VAC, 132,000 VAC and even 400,000 VAC. High voltages are often used in the electrical systems for power generation, power distribution, the rail network, petrochemical refineries, electrical service and maintenance industries.

While all electricity can be dangerous, the energy levels seen in high voltage systems represent a significant hazard. In addition to electrocution, serious burns can be received either by electricity flowing through the body or by arcing. Many people mistakenly believe that the only way to be harmed by electricity is if you touch live parts, but high voltage electricity is capable of traveling through the air, this effect is called arcing and can be seen during a thunder storm as lightning. It is for this reason that high voltage test equipment usually has long probes ensuring a safe distance between the user and the system under test.

Seaward’s high voltage test range is designed for use on power system voltages of up to 33kV and includes ergonomically designed portable neon and digital voltage indicators, capacitive voltage indicators, circuit phasing equipment, insulator leakage detectors and current clamps.

HOW TO CARRY OUT HIGH VOLTAGE TESTING?

There are many standards and procedures which related to high voltage testing, often these have been created by the generation company or distribution network operator and form the basis for their staff safety training. Earlier we mentioned the process of safe isolation and this basic practice forms the starting point for most high voltage training courses around the world. 

The safe isolation process consists of three stages; Prove that the indicator or detector works, prove that the system to be worked on is ‘dead’ and then finally re-prove the indicator or detector afterwards.

To prove that the detector or indicator is working we need to have a know source on which to test safely, this function is usually performed by a device call a ‘proving unit’ like Seaward’s PH3. The proving unit is a battery powered device that generates a high voltage which can then be used to test the operation of the detector or indication before and after proving dead. The three step safe isolation process is designed to reduce the risk of an incorrect reading, which could lead you to believe that a system is ‘dead’ when in fact it still poses a danger. This outcome could result from testing with a faulty detector or indicator which fails to light when connected to a ‘live’ circuit or even a detector or indicator which fails during the testing process. Only by proving before the test do we know that the detector or indicator is working and then by re-proving again afterwards do we know that it was still working at the time of test, giving us the confidence that the system is actually safe to work on.

To perform phasing tests it is first necessary to perform voltage detection to ensure that all phases are ‘live’ and operational, in earthed neutral system this is achieved by performing a test to earth using an appropriate voltage detector or indication, such as Seaward’s KD1E range. Measurements are then made between the line conductors of the two circuits to be connected. Where the two lines are in-phase no voltage difference will be detected, lines that are out of phase will have a voltage difference and this will be detected and the indicator will light. These tests are performed across all combinations of the line conductors to be paralleled to ensure that phasing is correct before connection. 

It is important to note that high voltage testing is extremely dangerous and should only be performed by competent persons who are fully instructed in the safe systems of work for the type of system being worked on. Never attempt any work on or near high voltage systems without the expressed permission of the system operator or owner.

WHY CARRY OUT HIGH VOLTAGE TESTING?

There are many forms of testing that can be carried out on high voltage systems, but by far the most common is voltage detection or voltage indication, this is the process of checking that a voltage is present or not in a particular part of a high voltage system. Although under some circumstances work is carried out on high voltage systems while they are ‘live’, it is usually a requirement that the system is made ‘dead’ by a process call safe isolation before any work is carried out on, or near high voltage systems. Voltage detectors or indicators are therefore required to confirm that there is no voltage present at the point of work, after safe isolation and before work is carried out.

Another high voltage testing application for which Seaward’s HV products are used is ‘Phasing’. Almost all supply networks operate using multiphase systems, generally 3 phase. In a 3 phase system three line conductors (L1, L2 & L3) are used, each out of phase with the other two conductors by 120°. It is crucial that correct polarity and phase rotation is maintained throughout the supply network from the point of generation all the way through to the point of utilisation. If correct phasing is not maintained there can be many dangerous consequences. For example a simple mistake which reverses the connection of two phases can cause certain types of electric motor to run in the opposite direction, not great if this motor is connected to a sewerage pump or conveyor belt. Scale this type of phasing error up to parts of the generation network and the results can be catastrophic. Phasing Sticks such as Seaward’s PR11, PR15 and PR33 can be used to test for correct phasing before connections are made.