18 Figure 5 – Test loop for branch connectors with main and branch conductors having equal cross-sections and linear resistances .... 3.11 insulation of a cable insulating materials in
Principle
Connectors must undergo 1,000 cycles of heating and cooling to assess their durability The cold resistance of these connectors will be measured at designated intervals to evaluate their effectiveness when paired with conductors under load.
Heat cycle and, short-circuit tests shall be made with alternating current
NOTE Direct current may be used for heat cycle only when agreed between customer and manufacturer.
Test arrangement
The test circuit shall be as shown in Figure 5, 6, 7 or 8
Figures 5, 6, 7, and 8 illustrate the test circuits for various connector types: main and branch connectors with equal cross-sections and linear resistances, main and branch connectors with unequal cross-sections and linear resistances, through connectors with either equal or unequal cross-sections and linear resistances, and terminal lugs.
EN 50483-6, section 8.4.3.1 outlines an optional immersion test for samples designed for use in saline environments If the manufacturer and customer agree to include this test, the heat cycle test must be adjusted to allow for the immersion of test samples during each cycle.
The test circuit may include sectioning joints so that it can be dismantled and short-circuit tests can be made easily
In Figure 6, the disconnection devices (X) are
• closed when the circuit is carrying heating current, and
• opened when resistance measurements and short-circuit applications are being made www.bab
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The sectioning joints shall be arranged and constructed so that they do not significantly affect the measurements
Phase and neutral conductors including reference conductors used in the test circuit shall remain insulated (except bare conductors)
5.2.4 Method of measuring ambient temperature
Accurate measurement of ambient temperature is crucial, ensuring it remains unaffected by the heat generated during testing This article presents a reliable method for achieving precise temperature readings, while also acknowledging that alternative approaches may be utilized.
Ambient temperature should be measured at the center of the test loop using a thermocouple, with its junction located in a polished metallic tube made from metal foil shaped into a cylinder The tube must have a height of 100 mm and a diameter ranging from 35 mm to 45 mm.
The thermocouple shall be located approximately at one third of the tube height from its upper end and fitted to it (e.g with a cross-support)
The test loop shall be installed in a location where the air is not disturbed The ambient temperature of the test location shall be between 15 °C and 30 °C
During the connector installation and resistance measurements, ambient temperature shall remain within the limits of (23 ± 3) °C and recorded
For stranded conductors, potential between the strands at measuring points can cause errors in measuring electrical resistance
Welded or soldered equalizers, as illustrated in Annex A, are essential for addressing the issue of uniform current distribution in the reference conductor These methods are recommended to guarantee reliable measurements.
NOTE Other methods may be used provided that they give comparable results and do not affect the temperature of the connectors or the reference conductor
Annex A provides details on the construction of welded equalizers
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5.2.7 Lengths and configurations of conducting paths
A 1 and A 2 cross-sections relative to conductivity of the conductors 1 and 2 in mm²
A, B potential points for measuring the potential difference between the extremities of the reference conductor corresponding to conductor of cross-section A 1
E, F potential points for measuring the potential difference between the extremities of the reference conductor corresponding to conductor of cross-section A 2
4 branch connector l ra distance between potential points A and B 5 sleeve connector l rb distance between potential points E and F
To measure the potential difference between points C and D on the connector, it is essential to consider the distances \( l_a \) and \( l_b \) from these points to the nearest surface of the connector body The values of \( l_a \) and \( l_b \) are influenced by the cross-section \( A \) of the corresponding conductor, as detailed in Table 1.
Figure 1 – Lengths and configurations of conducting paths www.ba ba a a a a a a a a a a a a b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a k k k k k k k e e e e c c c c c c c o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m
The conducting path lengths (see Figure 1, 5, 6, 7 or 8) shall comply with Table 1
If \( A_1 \neq A_2 \), then the cross-section of the reference conductor associated with \( A_1 \) is \( A_1 \), while the cross-section for the reference conductor related to \( A_2 \) is \( A_2 \) Both reference conductors will have an identical length given by \( l_r = l_a + l_b \).
Potential points shall be placed at a distance la and lb from the nearest surface of the connector body
The length of the conductor between connectors must be at least \(80 \sqrt{A}\) millimeters, with a minimum requirement of 500 millimeters For branch connectors, the value of \(A\) refers to the cross-section of the main conductor.
Where a test loop comprises of only one cross-section of conductor, a single reference conductor shall be used
Where a test loop comprises of more than one cross-section of conductor, one reference conductor shall be required for each cross-section
One (two) insulated length(s) of conductor(s) that constitute the heating loop shall be called the reference conductor(s); there shall be a potential point at each of its (their) extremities
The reference conductor shall not have its insulation removed if insulated In order to control the test a thermocouple shall be placed at the mid point of the reference conductor
The reference conductor shall be of sufficient length to prevent thermal interference from its end terminations
In the case of unequal cross-sections, both references conductors of lengths l ra and l rb shall reach the defined reference temperatures.
Test specimen
5.3.1 Setting up of the test loop
The conductors are designated by their cross-sections A₁ and A₂, ensuring that the resistance R₁ of conductor A₁ is lower than the resistance R₂ of conductor A₂.
Where R 1= R 2 then the conductor will be referred to by its cross-section A 1
Conductor resistances R 1 and R 2 are measured in the same periodicity as connector resistance www.babake.com
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Various types of test loops are defined in Figures 5 to 8
Where A 1 = A 2, the test loop shall consist of
• one conductor of cross-section A 1 with linear resistance R 1,
• one reference conductor of length l ra on cross-section A 1
Figure 5 shows the diagrammatic layout of the loop, where l = l a = l b
Where A 1 ≠ A 2, the test loop shall consist of
• one conductor of cross-section A 1 with linear resistance R 1,
• one conductor of cross-section A 2 with linear resistance R 2,
• one reference conductor of length l ra on cross-section A 1,
• one reference conductor of length l rb on cross-section A 2
Figure 6 shows the diagrammatic layout of the loop
The configuration and dimensions of the test loops shall be recorded
Two test loops shall be used for each type of connector as given in Table 2
Table 2 – Testing cross-sections of main and branch conductors
Loop Main conductor cross-section Branch conductor cross-section
2 nd loop max or min a min a The choice of max or min cross-section should be agreed between the customer and the manufacturer
5.3.2 Preparation of cables and cores before tests
New insulated cores or cables shall be used
The same core of a cable cross-section (e.g Phase 1), shall be used for the whole test
Insulated cores must undergo pre-conditioning to achieve dimensional stabilization of the insulating sheath It is essential to maintain the core sections in an enclosure at a temperature of (30 ± 2) K above the normal operating temperature of the conductor.
Annex C of EN 50483-1 for approximately 1 h and letting them cool down naturally to ambient temperature www.babake.com
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Connectors shall be installed according to the manufacturer’s installation instructions
A torque meter shall be used for all tightening operations The accuracy and resolution of the torque meter is given in EN 50483-1
The connectors shall be held in position during tightening
Connectors shall be tightened to the minimum manufacturer’s declared torque (connectors with shear head) or 90 % of the nominal manufacturer’s declared torque (connectors without shear head)
Tightening shall be realised in accordance with EN 50483-1, 9.1.8
The rate of tightening shall be in accordance with EN 50483-1, 9.1.10
A connector that allows for independent tightening of main pierced and branch stripped connections requires the branch stripped connection to be mounted four times and fully removed three times Prior to the initial installation, the branch conductor must be prepared, and this prepared end should be utilized throughout the testing process It is essential to maintain the orientation of the branch cable in relation to the connector.
Measurement
The temperature of a reference conductor or of a connector shall be measured with a thermocouple located at the point shown in Figure 2
Accuracy of temperature measurement shall be ± 2 K or better
Connectors must feature a small hole in the outer housing, enabling direct application of a thermocouple at the midpoint of the metallic current path between the connector and the connected conductors.
The hole shall be drilled so that the connector’s mechanical performance is not affected www.babake.com
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1 metallic current path 3 main conductor
2 thermocouple position 4 branch conductor a) Location of thermocouple in an IPC
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1 thermocouple 4 adhesive tape: thermocouple and insulation are covered with 2 half-lap layers adhesive tape
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For the reference conductor, the thermocouple should be placed as near as possible to the midpoint of the conductor It must be securely positioned by sliding it beneath the strands of the outer layer of a stranded conductor and under the cable insulation.
An equivalent method can be used
The resistance of connectors and reference conductors must be measured between two adjacent points using a direct current that does not exceed 10% of the nominal current (I_N) This process involves heat cycling to ensure a stable conductor temperature while measuring the voltage drop between the points The resistance value is calculated as the ratio of the voltage drop to the direct current used.
When measuring resistance, it is essential to document the reference conductors, connectors, direct current, and ambient temperatures in the test report Additionally, the temperatures of the reference conductors and connectors must not exceed the ambient temperature by more than 2 K.
• voltage measurements shall have an accuracy within ± 0,5 % or ± 10 μV, whichever is the greater;
• current measurements shall have an accuracy within ± 0,5 % or ± 0,1 A, whichever is the greater
• resistance measurements shall have an accuracy within ± 1 % or ± 0,5 μΩ, whichever is the greater when the instrument is calibrated against a certified standard resistance
NOTE Annex C provides recommendations to improve accuracy of measurement.
Heat cycle
Figure 3 diagrammatically represents the heat cycle curve
The object of the first heat cycle is to determine the reference conductor temperature to be used for subsequent cycles and also to identify the median connector
Current shall be circulated in the test loop, bringing the reference conductor to the temperature value (θR) At equilibrium the temperature θR shall be regulated between the normal operating temperatures
+5K as a minimum and the normal operating temperature
+10K as a maximum The normal operating temperature can be found in Annex C of
The median connector temperature shall be stable within 2 K for a minimum of 10 min
For through connectors with unequal cross-sections, the reference conductor is that associated with the smallest electrical cross-section
Main reference conductor and branch reference conductor shall be maintained within the temperature limit +5K and +15K for main and +5K and +10K for branch
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The temperature (θ R ) - time (t 1) heating profile determined in this way shall be recorded and used for all subsequent cycles The equilibrium current(s) I N shall be recorded in the test report
To shorten the heating time during the initial phase of the heating cycle (t 1-a), a higher current can be utilized The minimum duration for this increased current is specified in Table 3.
Table 3 – Minimum elevated current heating time
Nominal conductor cross-section area mm 2
After period t 1, there shall follow a period of cooling t 2.
The cooling rate must be regulated to ensure that the connector and reference conductor reach an ambient temperature of +5 K within a minimum of 10 minutes This cooling rate should be consistently maintained throughout the duration of the test.
Heating can be resumed when the connector and reference conductor temperature drops to 35 °C or lower, provided that the minimum cooling time has been met if cooling were to continue.
If accelerated cooling is used, it shall act on the whole of the loop, and use air within ambient temperature limits www.babake
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1 temperature axis 4 temperatures 35 °C for connectors and reference conductor
2 reference conductor temperature R 5 time axis
The total period t 1 + t 2 constitutes a heat cycle
A total of 1,000 heat cycles will be conducted, with resistance and temperature measurements taken for each connector and reference conductor after the specified cooling periods Additionally, the maximum temperature of each connector during the cycle immediately before or after the resistance measurements will be documented.
Measurements shall be made at the following cycles:
0 (before the first heat cycle only for resistance measurements)
0 (before the first heat cycle only for resistance measurements)
200, after short circuit Then every 75 cycles
A tolerance of ± 10 cycles shall be allowed www.babake.com
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5.5.3 Short-circuit tests (for Class A connectors only)
Six short-circuits shall be applied after the 200 th cycle
The short-circuit current must be sufficient to elevate the temperature of the reference conductor from its ambient state to at least the specified short-circuit temperature.
Annex C of EN 50483-1 The short circuit duration shall be short enough to be considered as adiabatic
For unequal cross-sections, the minimum current should be applied The short-circuit current duration is typically set at (1.00 ± 0.15) seconds If the short-circuit current requirement surpasses 25 kA, a duration of up to 5 seconds may be utilized, and this duration must be clearly specified.
After each short circuit, the test loop shall be cooled to a temperature ≤ 35 °C
The test loop can be disassembled for these tests, as the short-circuit test aims to generate thermal effects from high current To minimize electrodynamic forces, it is advisable to utilize a concentric return conductor, as illustrated in Figure 4.
The test arrangements shall be noted in the test report
1 connector under test 4 conductor connected to the metallic tube
2 main conductor 5 current flow through metallic tube
Figure 4 – Use of a concentric return conductor
The short circuit current can be calculated following IEC 60949:1988, Clause 3, and determined using Annex B to select the current required for a specific temperature rise, provided that the actual conductor cross-sectional area has been confirmed.
During assembly, transport, and handling, it is crucial to avoid bending or vibrations, as these can generate mechanical forces that negatively impact the contact resistance of the test objects.
Measuring the temperature specified in Annex C of EN 50483-1 can be challenging in practice It is acceptable to calculate the short circuit current and its duration, assuming that the short circuit temperature is reached when these values are utilized Since the critical value pertains to the energy delivered to the system, both the current and its duration can be adjusted within the necessary range, provided that the required energy quantity is achieved.
An individual connection resistance (R j) enables a common method of connector assessment to be made over the six connections The parameters listed below are calculated according to
The connection resistance (\(R_j\)) must be calculated for each of the six connectors across all specified measurement intervals Initially, the scatter (\(\delta\)) between the six initial \(R_j\) values, measured before heat cycling, should be determined Additionally, the mean scatter (\(\beta\)) of the six \(R_j\) values averaged over the last 11 measurement intervals needs to be calculated The assessment of resistance stability requires calculating the larger relative change in each connector's resistance over the last 11 measurements Furthermore, the resistance factor ratio (\(\lambda\)) should be computed, along with the stability of the connector's temperature Finally, the maximum temperature (\(\theta_{\text{max}}\)) for each connector must be recorded.
Requirements
The six connectors must meet the specifications outlined in Table 4 If any one of the connectors fails to meet these requirements, a new loop can be tested, ensuring that all six connectors comply with the necessary standards.
If any of the six connectors fail to meet one or more requirements, re-testing will not be allowed, and the connector type will be deemed non-compliant with the standard.
The resistance, referred to 20 °C, between measuring points spanning a connector, is:
The resistance, referred to 20 °C, of the reference conductor of cross-section A 1 is:
The resistance, referred to 20 °C, of the reference conductor of cross-section A 2 is:
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U CD is the voltage drop between measurement points of the connector;
U AB is the voltage drop between measurement points of reference conductor of cross-section A 1;
U EF is the voltage drop between measurement points of reference conductor of cross-section A 2; θ is the connector temperature while measuring resistances; θr is the reference conductor temperature while measuring resistances;
The resistance, denoted as R 20, is determined between two equalizers and adjusted to a temperature of 20 °C The variable la represents the distance from the connector to the equalizer for the A 1 conductor, while lb indicates the distance from the connector to the equalizer for the A 2 conductor.
R ra is the resistance of cross-section A 1 reference conductor and corrected to
R rb is the resistance of cross-section A 2 reference conductor and corrected to
20 °C; α is the coefficient of variation in resistivity with temperature for Al and Cu = 4,0 x 10 -3 K -1 , Al alloy = 3,6 x 10 -3 K -1
The scatter between the six values of R j (one value for each connector) at cycle zero shall be calculated as follows:
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6 δ 1 where t s is the Student coefficient; t s = 4,032 for 99 % two-sided confidence level and five degrees of freedom
Hence, the initial scatter is:
For each connector, its mean value over the interval x = -5 to +5 shall be calculated: ¦ +
Hence six values are obtained The mean of these six values shall be calculated: ¦
Hence, the mean scatter is:
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5.6.2.3 Assessment of resistance stability for each connector
For each connector, its mean value over the interval x = -5 to +5 shall be calculated ¦ + −
R = − Δ the resistance stability is given by the ratio j j
R j is the connector resistance for each connector found at any stage of the measurement series;
R j0 is the connector resistance of the same connector measured at cycle zero
For each connector, the temperature stability shall be estimated over the last
= Δ j j j θ θ where Δθ j = temperature difference between reference cable and connector
5.6.3.2 Maximum temperature of each connector
Each connector temperature, θ j shall be lower than or equal to the warmest reference conductor: θ j ≤θ R www.babake.com
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Assessment of resistance stability 15 % Resistance factor ratio λ 2,0 Temperature stability Δ θ j Δ − θ j 10 ≤ Δ ≤ Δ + θ j θ j 10
Maximum temperature θ j of each connector θ R
NOTE An explanation of the terms used in the preceding statistical analysis and background papers may be founded in EN 61238-1:2003
Key l a = l b = l and = l r = 2 l d conductor length between two connectors d 80 A or 500 mm minimum
1 reference conductor insulated between equalisers
Figure 5 – Test loop for branch connectors with main and branch conductors having equal cross-sections and linear resistances w w w w w w w w w w w w w w w w w w w w w w w w w w w w w w w w w ww.babake.c o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m
If the difference between the main and branch electrical cross-sections is greater than half a step as defined below, this test loop shall be used
Where the change is lower than or equal to half a step, Figure 5 shall be used
1 reference conductor A 2 R 2 insulated between equalisers
For branch cables with a cross-section less than 16 mm², the use of an impedance adapter may be waived if mutually agreed upon by the manufacturer and the customer In such instances, it is essential to ensure that only the branch conductor remains within the specified temperature limits.
2 reference conductor A 1 R 1 insulated between equalisers d conductor length between two connectors d 80 A or 500 mm minimum
A conductor cross-section (mm 2 ) 4 conductor A 2 R 2 insulated between equalisers p.p potential point 5 conductor A 1 R 1 insulated between equalisers
Figure 6 – Test loop for branch connectors with main and branch conductors having unequal cross-sections and linear resistances www ww w w b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k e.c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m
When the connectors have equal cross-section, then l a = l b and l ra = l rb 1 conductor A 1 R 1 insulated between equalisers d conductor length between two connectors d 80 A or 500 mm minimum
A = A 1 or A 2 - The largest conductor cross-section shall be used
3 reference conductor A 2 R 2 insulated between equalisers p.p potential point 4 connectors
TC thermocouple 5 reference conductor A 1 R 1 insulated between equalisers
6 thermocouple middle of the conductor
Figure 7 – Test loop for through connectors with conductors having equal or unequal cross-sections and linear resistances w w w w w w w.baba k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k e e e e e e e e e e e e e e e e e e e e e e e e e e e co o o o m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m m
Key l a = l b = l and = l r = 2l 1 reference conductor insulated between equalisers d conductor length between two connectors d 80 A or 500 mm minimum
2 thermocouple middle of the conductor
A conductor cross-section (mm 2 ) p.p potential point
TC thermocouple a) Test loop for pre-insulated lugs www.babake.com
1 intermediate part of material and cross-section identical to those of the connections palms:
2 nut and bolt p.p potential point b) Test loop for pre-insulated lugs – Lug connection detail
Figure 8 – Test loop for pre-insulated lugs www.babake.com
For stranded conductors, potential between the strands at measuring points may cause errors in measuring electrical resistance
Welded or soldered equalizers are effective solutions for achieving uniform current distribution in reference conductors, ensuring reliable measurements These methods are highly recommended for overcoming related issues.
Other methods may be used provided they give comparable results and do not affect the temperature of the connectors or the reference conductor
To properly join conductors, first cut them to a square shape and clean the ends Next, position the ends in contact on a support and solder them using silver solder, taking care to keep the conductor away from the ends cool to prevent any damage.
- apparatus for TIG (Tungsten Inert Gas) or MIG (Metal Inert Gas) welding;
- welding rod A5 (1 100), welding rod A5 (1 050) or equivalent
To prepare the conductors for welding, squarely cut and clean their ends, then use a welding torch to melt them For cables with cross-sectional areas exceeding 95 mm², first melt the periphery before adding weld metal to the center to finish the chamfer The dimensions for the chamfer length "a" and the separation "b" between the conductors for the final welding are crucial for a successful joint.
To achieve a uniform circular weld profile, position the conductors supported and spaced by dimensions "b" and build up the weld metal at the center It is crucial to keep the conductor away from the ends sufficiently cool to preserve its mechanical properties in the contact area For more information, visit www.babake.com.
The dimensions of the equalizer shall be as indicated in Table A.1 a) Ends prepared b) Welding/soldering support
The dimensions for potential points are defined as follows: for a cross-sectional area \( A \leq 95 \, \text{mm}^2 \), the length \( l_e \) should be between 10 mm and 15 mm; for \( 95 \, \text{mm}^2 < A \leq 240 \, \text{mm}^2 \), \( l_e \) should range from 15 mm to 25 mm; and for \( A > 240 \, \text{mm}^2 \), \( l_e \) should be between 25 mm and 35 mm Additionally, welded or soldered equalizers are referenced in Figure A.1.
Determination of the value of the short-circuit current
Figure B.1 – Diagram of short-circuit current
On the diagram giving the current as a function of time, the total time BT is divided into
10 equal parts and the value of the alternating current component is measured at the verticals at points 0, 1, 2, 10
These values are designated by I max0, I max1, I max2, I max10
I max is the maximum value of the alternating component of the current at each point
The equivalent r.m.s current during this time BT is given by:
NOTE 1 The direct current component (CC ’ ) is neglected
NOTE 2 This annex is consistent with EN 61238-1:2003 www.babake.com hort-ciort-c nction o nction ting cung cu ax0 0, , II ma ma
Recommendations to improve accuracy of measurement
Bending or vibrations during transport and handling may give rise to mechanical forces, which affect the contact resistance of the test objects and should be avoided
The same measuring points should be used throughout the test, since calculation always refers to the initial situation Verification of measuring points, especially after short-circuit test is advised
In the case of stranded conductors the distances between any equalizer in the test set up where no connectors are installed may be used for verification of resistance measurements
All recorded values should show that the equalizers have acceptable stability throughout the test
Check the validity of calibration or make a calibration of each instrument prior to the test
If possible, calibrate the whole measuring chain
Temperature readings may easily be checked at a temperature of 100 °C in boiling water and at 0 °C in ice water
For measuring the current, a calibrated shunt may be introduced into the test loop
If possible, use the same instrument for voltage (ΔU d.c.), current (ΔU d.c of a shunt) and temperature (ΔU d.c of thermocouple-voltage output) measurement
For accurate voltage measurement calibration or direct resistance measurement, a calibrated resistance with a corresponding value should be utilized It is essential to perform checks before, during, and after the testing process to ensure reliability.
• to use the same instruments during the whole test,
• to avoid whenever possible the replacement of any instrument or the change in the systematic uncertainty may influence the assessment of the measuring results,
• to use automatic storage of the measured values to avoid copy errors,
• to use a validated computer program for the calculation to avoid errors by accident
Every effort should be made to avoid spurious readings
Data of instrument performance should be given in the test report www.babake.com e aa tion of eon of e hain ain heckedecked ibratebrate
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IEC 60949:1988, Calculation of thermally permissible short-circuit currents, taking into account non-adiabatic heating effects www.babake.com