Transcript Bridge Measurements

Which one is the Proper Fault Location Method ?
Typical Cable Faults
Partly
flooded
cable
Insulation Faults
Totally
flooded
cable
Cb≠Ca
Rb≠Ra
Recommended Fault Location Method
Low level
▼
Murray
Active
Sensitive
▼
Küpfmüller
Active
Sensitive
Medium level DC
Active
Protected
Active
Protected
Medium level AC
Active
Protected
Active
Protected
High level AC
Passive
Passive
Disturbing Voltage
Intermittent
▼
3-Point (a-b)
Active
Sensitive
Active
Protected
Active
Protected
Passive
▼
3-Point
Active
Sensitive
▼
C unbalance
Active
Sensitive
▼
R difference
Active
Sensitive
Active
Protected
Active
Protected
Active
Protected
Active
Protected
Active
Protected
Active
Protected
Passive
Passive
Passive
Passive
Passive
Repeated
Küpfmüller
To learn more click on the selected method!
▼
Graaf
Graaf
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Disturbers
The expected disturbing voltage depends on:
A.) The function of neighboring pairs in the cable
Intermittent disturbing voltages are expected
if the neighboring pairs are used for POTS
DC disturbing voltage is expected if the
neighboring pairs are used only for ISDN
No disturbing voltage is expected if the
neighboring pairs are used only for data transfer
B.) The distance to electrical railway
High disturbing AC voltage is expected if the
cable is very close to the track
Low disturbing AC voltage is expected if the
cable is fare enough from the track
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Active Bridge Murray Method in Sensitive mode
Recommended when:
■ only one wire of a pair is faulty
■ the level of disturbing voltages are low
The Murray method consists of 2 measurements:
■ Measurement of disturbing voltages
■ Bridge measurement with strap on the far end
ECFL 30 automatically performs the 2 measurements with the help of the remote controlled switch ELC 30
The result of Murray measurement is: Lx/L
In addition ECFL 30 provides:
■ RL loop resistance
■ FaE insulation resistance
■ Rx resistance to fault
■ Lx distance to fault
The conditions of accurate results:
■ Ia and Ib < 450 uA
■ Ф wire a=Ф wire b
■ FbE>1000 x FaE
■ FbE>10 MOhm
If the disturbing voltages overload the input
repeat the measurement in Protected mode
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Active Bridge Murray Method in Protected mode
Recommended when:
■ only one wire of a pair is faulty
■ the level of disturbing voltages are medium
The Murray method consists of 2 measurements:
■ Measurement of disturbing voltages
■ Bridge measurement with strap on the far end
ECFL 30 automatically performs the 2 measurements with the help of the remote controlled switch ELC 30
The result of Murray measurement is: Lx/L
In addition ECFL 30 provides:
■ RL loop resistance
■ FaE insulation resistance
■ Rx resistance to fault
■ Lx distance to fault
The conditions of accurate results:
■ Ia and Ib < 7 mA
■ Ф wire a=Ф wire b
■ FbE>1000 x FaE
■ FbE>10 MOhm
If the disturbing voltages overload the input repeat
the measurement with the passive bridge of ECFL 30
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Passive Bridge Murray Method
Recommended when:
■ only one wire of a pair is faulty
■ the level of disturbing voltages are high
The Murray method requires manual bridge balancing with helipot M.
■ the measuring voltage is connected to the ground
■ wire a and wire b should be interconnected at the far end
The far end can be automatically closed/open with the help of the remote controlled switch ELC 30
The result of Murray measurement is: Lx/L
In addition ECFL 30 provides:
■ RL loop resistance
■ FaE insulation resistance
■ Rx resistance to fault
■ Lx distance to fault
The conditions of accurate results:
■ Ф wire a=Ф wire b
■ FbE>1000 x FaE
■ FbE>10 MOhm
If the disturbing voltages overload the input repeat
the measurement with the passive bridge of ECFL 30
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Active Bridge Küpfmüller Method in Sensitive mode
Recommended when:
■ booth wires of a pair are faulty
■ the level of disturbing voltages are low
The Küpfmüller method consists of 2 measurements:
■ First measurement with open far end
■ Second measurement with strap on the far end
ECFL 30 automatically performs the 2 measurements with the help of the remote controlled switch ELC 30
The result of Küpfmüller measurement is: Lx/L
In addition ECFL 30 provides:
■ RL loop resistance
■ FaE and FbE insulation resistances
■ Rx resistance to fault
■ Lx distance to fault
The conditions of accurate results:
■ Ia and Ib < 450 uA
■ Ф wire a=Ф wire b
■ 0,5>FaE / FbE>2
■ FaE + FbE>100 x R loop
If the disturbing voltages overload the input
repeat the measurement in Protected mode
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Active Bridge Küpfmüller Method in Protected mode
Recommended when:
■ booth wires of a pair are faulty
■ the level of disturbing voltages are medium
The Küpfmüller method consists of 2 measurements:
■ First measurement with open far end
■ Second measurement with strap on the far end
ECFL 30 automatically performs the 2 measurements with the help of the remote controlled switch ELC 30
The result of Küpfmüller measurement is: Lx/L
In addition ECFL 30 provides:
■ RL loop resistance
■ FaE and FbE insulation resistances
■ Rx resistance to fault
■ Lx distance to fault
The conditions of accurate results:
■ Ia and Ib < 7 mA
■ Ф wire a=Ф wire b
■ 0,5>FaE / FbE>2
■ FaE + FbE>100 x R loop
If the disturbing voltages overload the input repeat
the measurement with the passive bridge of ECFL 30
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Passive Bridge Küpfmüller Method
Recommended when:
■ booth wires of a pair are faulty
■ the level of disturbing voltages are high
The Küpfmüller method requires 2 manual bridge balancings with helipot M.
■ First balancing with open far end
■ Second balancing with strap on the far end
The far end can be automatically closed/open with the help of the remote controlled switch ELC 30
The result of Küpfmüller measurement is: Lx/L
In addition ECFL 30 provides:
■ RL loop resistance
■ FaE and FbE insulation resistances
■ Rx resistance to fault
■ Lx distance to fault
The conditions of accurate results:
■ Ф wire a=Ф wire b
■ 0,5>FaE / FbE>2
■ FaE + FbE>100 x R loop
In case of strongly intermittent disturbing voltages
repeat the measurement with the Graaf method
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Active Bridge Repeated Küpfmüller Method
Recommended when:
■ booth wires of a pair are faulty
■ the level of disturbing voltages are intermittent
That method is a sequence of repeated Küpfmüller
measurements consisting of 15 part measurements
alternating :
■ 8 measurements with open loop (L)
■ 7 measurements with closed loop (K)
The Lx/L results are displayed in
two columns and a histogram
The far end is automatically closed/open with the
help of the remote controlled switch ELC 30
When the sequence is completed ECFL 30 selects the acceptable Lx/L results and calculates the
average of the accepted results. The unacceptable results are omitted and marked with asterisks.
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Active Bridge 3-Point (a-b) Method in Sensitive mode
Recommended when:
■
■
■
■
the insulation between wires and ground is good
the insulation resistance between wires a and b is low
some healthy pairs are available
the level of disturbing voltages are low
Faulty pair
FaE
Healthy auxiliary wires
The 3-Point method consists of 3 measurements:
■ First measurement when the measuring voltage is connected to wire a
■ Second measurement when the measuring voltage is connected to the ground
■ Third measurement when the measuring voltage is connected to wire c
ECFL 30 automatically performs the 3 measurements with the help of the remote controlled switch ELC 30
The result of 3 Point measurement is: Lx/L
In addition ECFL 30 provides:
■ RL loop resistance
■ FaE insulation resistance
■ Rx resistance to fault
■ Lx distance to fault
The conditions of accurate results:
■ Ia and Ib < 450 uA
■ The insulation resistance of auxiliary wires must be
thousand time as high than that of the faulty one.
If the disturbing voltages overload the input
repeat the measurement in Protected mode
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Active Bridge 3-Point (a-b) Method in Protected mode
Recommended when:
■
■
■
■
the insulation between wires and ground is good
the insulation resistance between wires a and b is low
some healthy pairs are available
the level of disturbing voltages are medium
Faulty pair
FaE
Healthy auxiliary wires
The 3-Point method consists of 3 measurements:
■ First measurement when the measuring voltage is connected to wire a
■ Second measurement when the measuring voltage is connected to the ground
■ Third measurement when the measuring voltage is connected to wire c
ECFL 30 automatically performs the 3 measurements with the help of the remote controlled switch ELC 30
The result of 3 Point measurement is: Lx/L
In addition ECFL 30 provides:
■ RL loop resistance
■ FaE insulation resistance
■ Rx resistance to fault
■ Lx distance to fault
The conditions of accurate results:
■ Ia and Ib < 7mA
■ The insulation resistance of auxiliary wires must be
thousand time as high than that of the faulty one.
If the disturbing voltage overload the input repeat
the measurement with the passive bridge of ECFL 30
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Passive Bridge 3-Point (a-b) Method
Recommended when:
■
■
■
■
the insulation between wires and ground is good
the insulation resistance between wires a and b is low
some healthy pairs are available
the level of disturbing voltages are high
Faulty pair
FaE
Healthy auxiliary wires
The 3-Point method requires 3 manual bridge balancing with helipot M.
■ First balancing when the measuring voltage is connected to wire a
■ Second balancing when the measuring voltage is connected to the ground
■ Third balancing when the measuring voltage is connected to wire c
The far end can be automatically closed with the help of the remote controlled switch ELC 30
The result of 3 Point measurement is: Lx/L
In addition ECFL 30 provides:
■ RL loop resistance
■ FaE insulation resistance
■ Rx resistance to fault
■ Lx distance to fault
The condition of accurate results:
■ The insulation resistance of auxiliary wires must be
thousand time as high than that of the faulty one.
In case of strongly intermittent disturbing voltages
repeat the measurement with the Graaf method
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Active Bridge 3-Point Method in Sensitive mode
Recommended when:
■ the gauge of wires in a pair are different
■ some healthy pairs are available
■ the level of disturbing voltages are low
The 3-Point method consists of 3 measurements:
■ First measurement when the measuring voltage is connected to wire a
■ Second measurement when the measuring voltage is connected to the ground
■ Third measurement when the measuring voltage is connected to wire c
ECFL 30 automatically performs the 3 measurements with the help of the remote controlled switch ELC 30
The result of 3 Point measurement is: Lx/L
In addition ECFL 30 provides:
■ RL loop resistance
■ FaE insulation resistance
■ Rx resistance to fault
■ Lx distance to fault
The conditions of accurate results:
■ Ia and Ib < 450 uA
■ The insulation resistance of auxiliary wires must be
thousand time as high than that of the faulty one.
If the disturbing voltages overload the input
repeat the measurement in Protected mode
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Active Bridge 3-Point Method in Protected mode
Recommended when:
■ the gauge of wires in a pair are different
■ some healthy pairs are available
■ the level of disturbing voltages are medium
The 3-Point method consists of 3 measurements:
■ First measurement when the measuring voltage is connected to wire a
■ Second measurement when the measuring voltage is connected to the ground
■ Third measurement when the measuring voltage is connected to wire c
ECFL 30 automatically performs the 3 measurements with the help of the remote controlled switch ELC 30
The result of 3 Point measurement is: Lx/L
In addition ECFL 30 provides:
■ RL loop resistance
■ FaE insulation resistance
■ Rx resistance to fault
■ Lx distance to fault
The conditions of accurate results:
■ Ia and Ib < 7mA
■ The insulation resistance of auxiliary wires must be
thousand time as high than that of the faulty one.
If the disturbing voltage overload the input repeat
the measurement with the passive bridge of ECFL 30
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Passive Bridge 3-Point Method
Recommended when:
■ the gauge of wires in a pair are different
■ some healthy pairs are available
■ the level of disturbing voltages are high
The 3-Point method requires 3 manual bridge balancings with helipot M.
■ First balancing when the measuring voltage is connected to wire a
■ Second balancing when the measuring voltage is connected to the ground
■ Third balancing when the measuring voltage is connected to wire c
The far end can be automatically closed with the help of the remote controlled switch ELC 30
The result of 3 Point measurement is: Lx/L
In addition ECFL 30 provides:
■ RL loop resistance
■ FaE insulation resistance
■ Rx resistance to fault
■ Lx distance to fault
The condition of accurate results:
■ The insulation resistance of auxiliary wires must be
thousand time as high than that of the faulty one.
In case of strongly intermittent disturbing voltages
repeat the measurement with the Graaf method
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Synchronous Graaf Method
Recommended: for Fault Location of Totally Flooded Cables
Graaf method can be used when no other method is applicable due to disturbing DC currents.
That method is based on disturbing DC current measurement at the ends of the tested pair.
The location of fault is calculated from the rate of the measured DC currents (I1 / I2 )
The level of disturbing DC currents is usually intermittent. For the sake of proper test result
the master and slave instruments perform synchronous current measurements at the cable ends.
In this case the current rate ( I1 / I2 ) does not depend on the actual value of disturbing currents.
Notice: The current measuring method was invented by Dr Robert Van de Graaf in 1931
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The Original Graaf Method and its Problems
The Theory was perfect:
The result doesn't depend on the actual value of currents
But in the practice it was not satisfactory due to the following problems:
1.) The sensitivity and accuracy of available current meters were not enough at that time
2.) The reading of meters was strongly subjective in case of intermitting currents
ECFL 30 eliminates all the problems of the original Graaf method:
1.) The features of current meters are much better (Sensitivity:3 uA, Ri:1 Ohm, Accuracy: 0,3%)
2.) The master and slave instruments perform synchronous current measurements at the cable ends.
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Resistance Difference Measurement
The active bridge of ECFL 30 is accurate and comfortable
The passive bridge of ECFL 30 is disturbing voltage tolerant
ECFL 30 provides the following results: Ra, Rb, Rloop, Δ R,
%
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Capacitance Unbalance Measurement
The active bridge of ECFL 30 is accurate and comfortable
The passive bridge of ECFL 30 is disturbing voltage tolerant
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THANK YOU FOR YOUR
ATTENTION!