# What are the procedures to locate cable faults and Types of cable testing? **URL:** \ **Category:** Electrical\ **Tags:** cable\ **Created:** [August 2, 2019, 4:38pm UTC](https://forumautomation.com/t/what-are-the-procedures-to-locate-cable-faults-and-types-of-cable-testing/6903 "2019-08-02T16:38:02Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![ashlin](https://forumautomation.com/user_avatar/forumautomation.com/ashlin/32/3775_2.png) [@ashlin](https://forumautomation.com/u/ashlin)\ **Post date:** [August 2, 2019, 4:38pm UTC](https://forumautomation.com/t/what-are-the-procedures-to-locate-cable-faults-and-types-of-cable-testing/6903/1 "2019-08-02T16:38:03Z")
**Why Cable testing is needed** The power supply networks are growing continuously so the quality of [power cables](https://forumautomation.com/t/cable-testing-general-test-for-high-voltage-and-low-voltage/3984) is an important factor. Cable testing must be done so that we could determine the condition of the power system, so by this, we could detect cable failures and we can improve the system reliability. Cable components ![image](https://cdn.forumautomation.com/original/2X/6/600e1a68cc44c73f8810b4be7a8adbb6dd71a620.jpeg) **Power cable testing** High voltage DC withstand test is the most common method of [cable testing](https://forumautomation.com/t/megger-test-sheath-resistance-test-procedure-for-cables/2549), this test can only detect defects which are associated with the conduction, so the defects were detected by the leakage currents The most common fault in dielectric cables is due to ‘partial discharge’ to perform the partial discharge test the equipment used was very expensive so acoustic equipment are used to do the partial discharge test **Types of cables and their characteristics** Cables can be classified into low, medium and high voltage cables, so according to the cable types the testing and maintenance are done, three-conductor cable has been used in the lower voltage range. Nowadays we use XLPE insulated because of the quality of the insulation material and it is well designed Due to these features, these cables can be used for extra-high voltage level ![image](https://cdn.forumautomation.com/original/2X/b/b8c825228d78d8b90c73430ab64a0dcc59745533.jpeg) **What are the procedures for cable fault location** These are the following steps to locate the cable faults - Fault indication - Disconnecting and Earthing - Fault analyses and insulation test - Cable fault Pre location - Cable route tracing - Precise cable fault location - Cable identification - Fault marking and repair - Cable testing and diagnosis **Cable testing** **Installation acceptance and maintenance test** - Installation test is a test which is done after cable installation but it is done before the application of joints or terminations - Acceptance test is also a field test which is conducted after [cable installation](https://automationforum.co/instrument-cable-installation-termination-considerations/), which is inclusive of terminations and joints before the cable system is commissioned - Maintenance test this test is done during the operation life of the cable system Thermal imaging camera is used for maintenance testing and a Megger for DC high pot testing ![image](https://cdn.forumautomation.com/original/2X/7/7c2f7d75da5e4a8a8a36a8df9ed1e707f6731a87.png) **Withstand test** This type of test involves the application of a voltage at a nominal level or higher than the prescribed period of time. By doing this test we could determine the cable’s ability to withstand voltage without insulation breakdown **Dielectric response** This kind of test is done to determine the cables dielectric response to the applied electric field, it can be done by measuring properties such as recovery voltage DC leakage current, dissipation factor This can be done by applying AC or DAC voltage for a prescribed period at a frequency of 20 – 300 Hz Advantages - An overall assessment of the cable can be done - Has the ability to detect the degree of water treeing and conductive type defects **Dielectric response – Dissipation factor** This could determine the loss factor of cables insulation, the loss factor will increase with age, so dissipation factor or Tan delta measurement can be used to determine the cable condition ![image](https://cdn.forumautomation.com/original/2X/a/a2271e59654374e002a0aa8dee523b65cca298dd.png) **Dielectric response – DC leakage current** During this test, a DC voltage lower than the withstand voltage is applied between the conductor and the insulation shield. So the leakage current through the cable insulation can be measured While testing extruded cable system HVDC must not be used leakage current measurement will only take place when the applied voltage reached its steady-state value **Dielectric Response – Recovery voltage** DC voltage is used to charge the cable for a specified time in this test, after that the cable will be discharged to ground through a resistor for short time and then the open circuit voltage is recorded and plotted against time It is used to determine the level of water tree degradation in extruded insulation **Partial discharge - Acoustic measurements** When a partial discharge occurs energy is released which produces a mechanical wave so the place in which partial discharge occurs acts like an acoustic wave source **Time-domain Reflectometry** This method uses changes in impedance of cable to determine cable imperfections such as faults, open connections, poor neutral, lossy connections, and water ingress