1 EXPERIENCE AND RELIABILITY

2 Short circuit loop measurements EN EN

3 EN Legal requirements The HD :2008 standard defines two types of inspections: –acceptance inspections; –periodic inspections. According to this standard, every system must be inspected during assembly, after assembly and before handover to the user. The acceptance inspection must include comparison of the measurements results with the relevant criteria defined, among others in the multi-sheet IEC standard, so as to check if the requirements given there have been met. In the case of enlargement or modifications of existing systems, the same full scope of tests must be performed as in the case of a new system.

4 EN Legal requirements During the performance of the measurements, precautions must be observed to make sure that the inspection will not cause a hazard to persons or pets and that it will not cause damage to the property and equipment even if the tested loop is defective. The person performing the inspection should be properly qualified and competent with regards to inspections. It must be emphasized that the person performing the inspection is responsible for preparing the system for tests, for conducting the tests, and for proper assessment of the test results (E and D license). An acceptance inspection consists of a visual inspection and a test. A visual inspection must be performed before the test, before the power supply of the system is switched on. A periodic test consists of activities necessary to determine if the system and all its components are in a condition that enables their continued operation.

5 EN Frequency of periodic inspections

6 EN Selection of measuring instruments The measuring instruments and devices must be selected in compliance with the respective parts of the EN standard: –EN Part 1 „General requirements” –EN Part 2 „Insulation resistance” –EN Part 3 „Loop impedance” –EN Part 4 „Resistance of earth connection and equipotential bonding” –EN Part 5 „Resistance to earth” –EN Part 6 „Effectiveness of residual current devices (RCD) in TT, TN and IT systems” –EN Part 7 „Phase sequence” –EN Part 10 „Combined measuring equipment for testing, measuring or monitoring of protective measures”

7 EN Permissible values of measurement errors Permissible values of measurement errors acc. to the EN standard

8 EN Permissible values of measurement errors Displayed value Error „±2%m.w” Error „± 4 digits” Error summary Summary error in % for particular measurement 1,00Ω0,02Ω0,04Ω0,06Ω6% 0,50Ω0,01Ω0,04Ω0,05Ω10% 0,20Ω0,00Ω0,04Ω 20% 0,13Ω0,00Ω0,04Ω 30% 0,10Ω0,00Ω0,04Ω 40% 0,05Ω0,00Ω0,04Ω 80% (exemplary meter with resolution 0,01Ω and basic error ± 2% m.w. ± 4 digits)

9 EN Categories of measuring instruments CAT IV – measurements performed at a low-voltage system source; examples are measurements of equipment at overcurrent protection devices; CAT III – measurements performed in systems in buildings; examples are measurements performed at distribution boards, automatic switches, electrical system conductors, to include cables, busbars, connectors, power outlets in systems and equipment intended for industrial applications and other equipment, e.g. fixed motors permanently connected with to stationary systems; CAT II – measurements performed in circuits that are directly connected with low-voltage systems; examples are measurements in home appliances, portable tools, etc.; CAT I – measurements performed in circuits that are not connected directly to a power supply system.

10 Short circuit loop measurements Z B Human body impedance R S Floor and shoes resistance R E Earthing resistance of accessible conductive parts I f Noise current U c Touch voltage U s Voltage drop on the floor/shoes resistance U f Noise voltage (U f =U c +U s ) Electrical installation scheme in the case of failure

11 Basic security – insulation of active parts, covers and fencing –Constant insulation or gas insulation with casing or separation –Access difficulties in places with qualified personnel supervision Security in case of fault – earthings, equipotential bondings, automatic power shutdown Additional source of security – RCD EN Automatic power shutdown

12 EN Automatic power shutdown – disconnection times

13 Short-circuit loop ( TN system) EN Automatic power shutdown – disconnection times

14 Short-circuit loop ( TT system) EN Automatic power shutdown – disconnection times

15 Measurement of touch voltage U ST EN Automatic power shutdown – touch voltage Voltage between energized object and the feet of the person in contact with the object

16 Measurement of shock voltage U T EN Automatic power shutdown – shock voltage

17 Loop measurements L-PE, L-N and L-L Measurement of impedance in protective circuit (L-PE) using two-pole method

18 Loop measurements L-PE, L-N and L-L Measurement of impedance in L-N circuit using two-pole method Measurement of impedance in L-L circuit using two-pole method

19 Relationship between the network voltage and the ability to calculate the prospective short-circuit current (PSC) Calculation of short circuit current according to U n and to U o

20 Zs and Rs Short circuit loop measurements Short-circuit loop impedance meters Z-impedance R-resistance X-reactance R X Z

21 Loop measurement for network diagnosis Loop measurements to determine aging of the network –comparing results of measurements after each period Big test current – diagnosis of diameter of cable

22 Big test current and 4-wire method – big accuracy Four-pole method - theory

23 Big test current and 4-wire method – big accuracy Measurement of impedance in TN- system

24 Measurement rules and meter connection scheme Short circuit loop measurements in networks secured with RCD

25 T h e A r t o f E l e c t i c a l M e a s u r e m e n t T h a n k y o u f o r y o u r a t t e n t i o n MEASUREMENT INSTRUMENTS