M.I. Cable High Resistance Fault Locator

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1 M.I. Cable High Resistance

2 M.I. Cable High Resistance Cable Health and Safety at Work This product, when used in normal or prescribed applications within the parameters specified for mechanical and electrical performance, will not cause danger or hazard to health or safety, provided that normal engineering and safety practices are observed and such products are used only by suitably trained persons. This product must be used in accordance with this Operating Manual There is no user adjustable or service components housed within the instrument. Introduction This manual is a guide to the operation of the High Resistance. The instrument is equally suitable for use in the factory or on site to locate faults in an installed cable system. The instrument incorporates a solid-state galvanometer with a backlight and adjustable sensitivity. The instrument is housed in a rugged case manufactured from a high impact co-polymer The instrument has been designed to meet the requirements of cable testing and locating cable faults where the resistance ranges from zero to 100MΩ. Faults can be between two conductors or between a conductor and its metallic sheath, concentric neutral, or earth. By employing a detection circuit of high input resistance it is possible to locate high resistance faults without the loss of sensitivity. A ten-turn potentiometer control is provided which indicates the fault position as a percentage of the total loop length. If both ends of the faulty conductor are not accessible at the test end then a good conductor of the same cross-sectional area is required. If the good conductor is of a different size then a conversion factor may be used to calculate an equivalent loop length, or a pair of healthy conductors may be used in which case the resistance is not critical. Technical Specification Power Supply for Instrument (Internal) Power Supply for Bridge Network (External) Size 90 x 110 x 60 mm Weight 0.7 kg including rubber protection boot 4 x 1.5 V battery, AA or equivalent A 6V rechargeable battery is provided to suit the cable under test. The following leads are included to enable the fault locations to be carried out. The Yellow lead is used to make the connection from the cable sheath to the instrument. The Red lead is used to connect one end of the faulty conductor to the Red conductor terminal on the instrument and to one side of the external battery. The Black lead is used to connect the other end of the conductor or second conductor to the Black conductor terminal and the other side of the external battery. With this bridge arrangement, faults having resistances up to 100 MΩ can be located with an accuracy well within +0.5% of the loop length. The instrument is contained within a plastic housing fitted with a protective rubber boot.

3 Connections WARNING Do not connect this instrument to a live or charged cable. Ensure that the cable to be tested has been completely discharged and earthed and that all normal safety procedures have been followed. To prevent post -charging, such as may take place after a DC voltage or insulation resistance test, ensure that the cable has been earthed for an adequate length of time before connecting the instrument. Connections to a faulty cable on a drum or ring circuit Both ends of the faulty conductor are accessible at the test end. This is the case during cable manufacture or when the cable is on a cable drum, or forms a ring circuit. The following connection arrangements should be made (see figures 1 and 2). 1 Prepare the cable ends by stripping back the sheath at each end and expose approximately 50 mm of conductor and clean to remove surface impurities. 2 The leads provided (Red and Black) are terminated with 4mm Banana plug at each end and with crocodile clips for connection to the cable conductors. The other end is supplied with a connector for connection to the external battery. Connect both crocodile clips from the Red lead to the cable conductor at one end, connect both crocodile clips from the Black lead to the other end of the cable conductor. Connect the 4 mm connectors to the Red and Black CONDUCTOR terminals on the Instrument. 3 Connect the crocodile clip of the Yellow lead to the cable sheath, and the 4 mm connector on this lead to the SHEATH terminal on the bridge. If the fault is not to the metallic sheath but to another conductor, then connect the crocodile clip to this conductor, and earth it if necessary. 4 Connect one of the connectors to a suitable battery. If the cable resistance is very low it may be advisable to limit the bridge network current by connecting a suitable resistance in series with this lead, e.g. a 1 Ω 100 W resistor will limit the current from a 6V battery to 6A, which should give adequate sensitivity. Fault Location i) With all the connections made, switch on the cable fault locator and allow the instrument to settle. Select the sensitivity as appropriate to the cable under test. ii) iii) iv) By means of the zero controls adjust the instrument until the solid-state galvanometer reads zero. Connect the second current lead to the battery. Adjust the main dial for zero reading on the solid-state galvanometer. The reading of the main dial then indicates the location of the fault as a percentage of the total length of cable loop from the end connected to the "+" (Red) terminal on the instrument. v) Reverse the connections to the conductor terminals and rebalance. The sum of the readings obtained in (iv) and (v) should add to approximately 100%. If the sum of the two readings differs substantially from 100% there is most likely more than one fault in the cable

4 Connection Methods When both ends of the fault conductor are together, Where the cable is on a reel. (Fig.1 and Fig.2) Fig 1 Fault to cable sheath with both ends accessible at the same point -- Sheath + Fig 2 Fault in other conductor with both ends accessible at the same point Fault -- Sheath +

5 Fig 3 Both ends are not accessible at the same point A good conductor of the same size is used as the return connection Good Conductor Faulty Conductor Other Conductor or Cable Sheath Fault -- Sheath + This method effectively doubles the length of the faulty conductor and reduces the accuracy by 50% Note: The total length of the cable loop means the total length of cable between the potential points that is the points at which the leads to the terminals of the instrument are connected to the cable. This is equal to the length of the cable in the case shown in Figs. 1 and 2 but is equal to twice the length of cable in the case shown in Fig. 3.

The is supplied with a Check Box to check the operation and general accuracy of measurement.

Test Procedure i) Connect the to the Test Box, Red to Red, Black to Black and Yellow to Yellow. ii) Connect an additional Black wire to the external battery negative terminal.

By means of the zero controls adjust the instrument until the solid-state galvanometer reads zero. v) Connect the second current lead to the battery.

The reading of the main dial then indicates the % distance to the fault from the end connected to the "+" (Red) terminal on the instrument.

6 The is supplied with a Check Box to check the operation and general accuracy of measurement. A selector switch is used to set various ratios between 0 and 100% The connections are colour coded, Red, Yellow and Black to match the. Test Procedure i) Connect the to the Test Box, Red to Red, Black to Black and Yellow to Yellow. ii) Connect an additional Black wire to the external battery negative terminal. iii) iv) Switch on the cable fault locator and allow the instrument to settle. Select the sensitivity and % Distance to Fault as required. By means of the zero controls adjust the instrument until the solid-state galvanometer reads zero. v) Connect the second current lead to the battery. vi) vii) Adjust the main dial for zero reading on the solid-state galvanometer. The reading of the main dial then indicates the % distance to the fault from the end connected to the "+" (Red) terminal on the instrument. The main dial and the Test Box selector should indicate the same value. Repeat the procedure for other Test Box settings. The Low sensitivity setting will show some hysterisis either side of the galvanometer null resulting is small differences between the indication and the setting. The most accurate values will be indicated when the High sensitivity is selected. MICC Ltd Unit 21 Sedling Road Wear East Industrial Estate Washington, Tyne & Wear NE38 9BZ Tel: +44 (0) Fax: +44 (0)

Instruction Manual for Digital Grounding Resistance Meter. Table of Contents

Instruction Manual for Digital Grounding Resistance Meter. Table of Contents I. Overview...2 II. Open-case Inspection...3 III. Safety Precautions...4 IV. Work Principle...7 V. Appearance Description...9 VI. Technical Characteristics 10 VII. Resistance Measurement Method..12 VIII.Battery