Special edition paper

Development of the Ground Fault

Protective Relay That Uses
No Auxiliary Energizing Source Masami Hino* Akira Horiguchi*

DC high voltage ground fault relays (ground fault protective relays) equipped to DC railway substations are devices to monitor the voltage
between the grounding mat of the substation and rails. If a ground fault occurs within a substation, they also detect the voltage rise and
immediately send out an open command to related circuit breakers to stop the supply of power to the point of the ground fault. However,
some ground faults can cause damage to surrounding facilities as well as the point of the accident. At the same time, they could also
possibly hamper ground fault protection due to contact faults with auxiliary energizing sources. We have therefore conducted development
of a ground fault protective relay that needs no auxiliary energizing source (DC 110V) to achieve a protection system where power supply is
stopped without fail in case of ground faults. We have thus-far finished production of a prototype and confirmed that the target performance
has been met, including stable output of that prototype even for unstable input voltage that modeled ground faults. This article will introduce
the development results.

● Keywords: DC feeding protection, DC ground fault, Contact fault, DC high voltage ground fault relay, Using no auxiliary energizing source

1 Introduction AC circuit breaker

(52)

Transformer
A DC high voltage ground fault relay (64P), one of the feeding
Rectifier
protection systems of DC railway substations, is a device for
monitoring the voltage (the difference in potential) between the
grounding mat of the substation and the return wire corresponding
DC high speed
to the rail. If a ground fault occurs within a substation, it also detects circuit breaker
(54F)
the voltage rise and immediately sends out an open command to Return wire
Feeder
related circuit breakers to stop the supply of power to the point of
Contact wire
the ground fault. However, some ground faults can cause damage Rail

to surrounding facilities as well as the point of the accident. At the

Fig. 1 Overview of DC Feeding System
same time, they could also possibly hamper ground fault protection
due to contact fault with auxiliary energizing sources, spreading the 2.2 DC Feeding Protection System
damage. A highly reliable feeding protection system needs to be built to
We have therefore conducted development of a ground fault minimize disruption of train operation in case of ground faults or
protective relay that needs no auxiliary energizing source (DC 110V) short circuit faults within a substation or along a line.
to drive the protection device with an aim of improving reliability of Fig. 2 shows an overview of a DC feeding protection system. The
ground fault protection. main protective relays (devices) used for DC feeding protection
systems are as follows.

Feeding Protection System

2 of DC Railway Substations

2.1 DC Feeding System

In a DC feeding system, DC 1,500V (standard voltage) stepped
down from 66kV special high voltage and rectified by a rectifier
at substations is supplied to feeders and contact wires as shown
in Fig. 1. This is done at substations set up at intervals of a few Interlinked
breaking equipment
kilometers to approx. 10 km (the higher the transport density, the (to the opposite
substation)
shorter the interval). The adjacent substations supply the power Grounding
mat Feeder/Contact wire
required for train operation in parallel. This is called a “parallel
feeding system”. Rail

Fig. 2 Overview of DC Feeding Protection System

* Technical Center, Research and Development Center of JR East Group JR EAST Technical Review-No.13 55
 Special edition paper
(1) DC high speed circuit breaker (54F) substation, the potential difference between the grounding mat and
This is a circuit breaker that can switch on and off the normal the standard grounding shows no change. So, only the 64P element
feeding circuits and also detect overcurrent of the feeding circuit with between the grounding mat and the rails operates to determine that a
the circuit breaker itself to rapidly breaking the circuit. ground fault is outside a substation, as the conventional 64P does.
(2) Fault selective device for feeding circuit (50F)
Using the difference between the current change (ΔI) of load current
and that of fault current, this selector detects a sharp change of
64P 64B
current in faults and sends out a breaking signal to just the damaged
Ground fault within
Operates Operates
feeder line. a substation
Voltage Ground fault outside Does not
(3) Interlinked breaking device monitoring Operates
Ground fault of a substation operate
within
As the direct current feeding system employs a parallel feeding a substation

system, sometimes it is difficult to detect a fault at the opposite

substation when a feeding fault occurs near a substation. So, when a
Ground fault outside
fault is detected and the circuit broken at a substation, the interlinked Grounding of a substation
Standard mat
grounding
breaker sends out a breaking signal to the high-speed circuit breaker Feeder/
Contact wire
Ground
of the opposite line of the next substation to ensure that power is cut Rail

off for the section where the fault occurs.

Fig. 3 Overview of 64PB
(4) DC high voltage ground fault relay (64P)
This relay detects the potential rise between the grounding mat
and the rails in a ground fault within a substation and sends out
Overview of the Development of the Ground Fault
a breaking command to DC high-speed circuit breakers and AC 4 Protective Relay Using No Auxiliary Energizing Source
circuit breakers. It also locks input circuits of the circuit breakers to
prevent the circuit breakers from being switched on before on-site Fig. 4 shows a system overview of the developed ground fault
check. Furthermore, it makes a breaking command for the opposite protective relay using no auxiliary energizing source. The presently
line of the next substation using interlocked breaking equipment to used protecting device requires an auxiliary energizing source (DC
immediately stop power supply to the point of the ground fault. 110V) to drive the logic unit of the device. So, in some ground
In order to limit the area where transport is affected when the faults, there is a risk of contact fault between the auxiliary energizing
relay is operated, JR East uses the 64P that has a function for source and DC 1,500V power supply occurring, hampering ground
distinguishing faults within or outside a substation (64PB). fault protection. We have therefore developed a ground fault
Since power is cut in a wide area in operation of a 64PB, the protective relay using no auxiliary energizing source that requires no
operating time of the 64PB is set based on the detection and external power supply to ensure protection even in case of a contact
operating time of the 50F that can select the damaged line and fault. Instead of an external auxiliary energizing source, we have
the breaking time of the opposite line by the interlinked breaking applied a power supply system where the relay supplies required
equipment (to wait for the protection time by a 50F) for faults power itself using the overvoltage between the grounding mat and
outside of a substation. the rails to be monitored.

The issue is to supply stable

(Developed relay) power to enable stable

Overview of the Operation of DC High

operation of the logic unit

3
Voltage between
grounding mat 1) Power unit

Voltage Ground Fault Relay and rails

Unstable power Power
supply
Stable power

A 64P is a relay that monitors the voltage between the grounding mat Rail

Ground fault within

and the rails and operates when the voltage in a fault exceeds a setting Grounding mat
Voltage
detector
Logic unit a substation
Ground fault outside
of a substation of a substation
value. The value can be set at three taps of 400V, 500V or 600V, and Standard 2) Detection and logic unit
grounding
JR East usually sets at 500V. A 64PB, which can distinguish faults (Existing relay)
DC relay
within or outside of a substation, is a 64P relay with the newly added Rail

Ground fault within

Voltage Logic
function of a 64B that monitors the potential difference between the Grounding mat
detector unit
a substation
Ground fault outside
of a substation of a substation

grounding mat and the standard grounding by setting the latter to Standard
grounding Auxiliary energizing source DC 110V

show a significant potential difference to that of the grounding mat

in case of ground faults within a substation (Fig. 3). 64B can be set Fig. 4 Overview of the Developed Relay
at three taps of 30V, 40V or 50V. (Comparison to the Existing Relay)
In a ground fault within a substation, the potential of the
grounding mat increases and the 64P (P element) that monitors the The relay device consists of two units: a power supply unit that
potential difference between the grounding mat and the rails operates. supplies stable power to the logic unit through a constant voltage
At the same time, the 64B (B element) between the grounding mat circuit and a detection, and logic unit that determines if ground
and the standard grounding operates to determine that a ground faults are within or outside of a substation.
fault is within a substation. In case of a ground fault outside of a

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The most important issue in this development was how to create

stable power to appropriately drive the logic unit from the voltage
between the grounding mat and the rails that fluctuates with arcing.
So, we first made a simple power unit prototype (Fig. 4 (1)) and
then developed the ground fault protective relay integrated with
detection and logic units based on the performance verification of
the prototype.

5 Development of the Power Unit

5.1 Main Specs of the Power Unit

The main specs of the power unit are as follows.
(1) The power unit outputs 10V drive voltage for the logic unit of the Fig. 5 Appearance of the Power Unit
ground fault protective relay to the voltage between the grounding
mat and the rails (input voltage). For the 200V or higher input
voltage that is half the 400V voltage set as the minimum criteria

Output voltage
for judging of a ground fault, the power unit outputs 10V
without fail.
(2) Overvoltage input withstand between the grounding mat and the
rails is to be 2kVDC for 1 minute.
(3) The power unit is to always be used together with a JEC-2500
power supply protective relay and have the insulation performance
(insulating resistance, commercial frequency withstand voltage,
lightning impulse withstand voltage) listed in Table 1.
The reason why we employed 200V or higher input voltage in Input voltage
spec (1) above is that we considered that value the risk area of a
Fig. 6 Characteristic Diagram of a Constant Voltage Circuit
ground fault. The power supply unit is to secure power at 200V
and instantly carry out calculation when reaching the setting value
(400V).
5.2 In-Factory Tests of the Power Unit
Table 1 Insulation Performance of the Power Unit To check the basic performance of the developed power supply unit,
Item
we carried out the following in-factory tests, achieving results where
Power-frequency
Insulating Lightning impulse
resistance
withstand voltage
withstand voltage specifications were met.
Applied to AC 50Hz 1 min.
(1) Input/output voltage characteristics:
All terminals of main
circuit - Between all 1,000V mega Characteristics of the output voltage to the change in input
output terminals and 50MΩ or greater 5,000V 4,500V
grounding voltage
Between all output 500V mega
terminals and 10MΩ or greater 2,000V 4,500V (2) Load characteristics:
grounding
Characteristics of the output voltage to the change in output
(load) current
Fig. 5 shows the appearance of the developed power unit. Table 2 (3) Output response characteristics:
shows the approximate size and weight of the unit. Rise characteristics of the output voltage in change of load
capacity
Table 2 Size and Weight of the Power Unit (4) AC input test:
Check of non-operation by AC input
Length Width Depth Weight
(5) Lightning impulse test:
190 mm 210 mm 230 mm 1.5 kg
Check of the insulation performance against lightning impulse
(6) DC 2kV input test:
The developed power unit consists mainly of a pressure dividing Check of overvoltage withstand for the input voltage
circuit, a constant voltage circuit using Zener diodes and an (7) Heat cycle test:
insulation circuit that ensures insulation between input and output. Performing above-mentioned tests after changing temperature
As shown in Fig. 6, the constant voltage circuit is a circuit that (–10ºC – 50ºC) and humidity in a constant temperature bath in
increases the output voltage proportionally until the input voltage a fixed cycle
reaches a set value (200V for this power supply unit) and outputs a
constant value (10V) once the input voltage exceeds a set value.

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5.3 Performance Tests of the Power Unit Output voltage

Since stability of the output voltage in relation to unstable input

voltage that fluctuates with arcing cannot be checked in in-factory

Output voltage (V)

Input voltage (V)
tests, we checked that in performance tests.
Fig. 7 and 8 show overviews of the test power circuit and the arc Input voltage involving arcing

test circuit used in the power unit performance tests.

Using an arc tester (a pantograph contact strip elevator) in the Threshold for establishing
output voltage 200V
large current testing building of the Research and Development
Center of JR East Group, we artificially made a gap between the
contact strip and the contact wire to generate an arc1) and fluctuate Time (s)

input voltage. Combining the power supply circuit with resistance, Fig. 9 Test Results of the Power Unit
that test machine allows continuous burn-in tests up to DC 1,800V
and 1,000A.
Development of the Ground Fault Protective
The input voltage to the power unit is the value achieved when the 6 Relay That Uses No Auxiliary Energizing Source
arc voltage generated by arcing is subtracted from DC 900V.
We used a voltage divider (400:1) to transform high voltage such as As explained in Chapter 5 above, we confirmed that stable output to
input voltage to the voltage appropriate to the voltage measurement drive the logic unit was achieved even in relation to unstable input
device and conducted measurements. voltage; thus, we conducted development of a ground fault protective
relay that uses no auxiliary energizing source and integrates the power
unit and the detection and logic unit.
Transformer Rectifier

6.1 Main Specs of the Ground Fault Protective Relay That

Uses No Auxiliary Energizing Source
Pantograph contact The developed ground fault protective relay can distinguish between
strip elevator and
contact wire ground faults within or outside of a substation as is done by existing
relays. The developed relay has the taps for the P element that
Combination with a monitors the voltage between the grounding mat and the rails (400V,
9Ω resistor (1.8 – 9Ω) 500V, 600V) and taps for the B element that monitors the voltage
Motor Generator
between the grounding mat and the standard grounding (30V, 40V,
Fig. 7 Test Power Circuit 50V). When input voltage exceeds the setting value of the individual
tap, the corresponding element works to determine whether the
To power supply (negative) ground fault occurs within or outside of the substation, based on the
criteria in Table 3.

Table 3 Determination Criteria for Ground Faults within or

Pantograph contact
Outside of a Substation and Operating Time
strip elevator
P element B element Operating time
Ground fault within Operates Operates 15ms
Contact wire
a substation
From power supply (positive) voltage
64P
(M)
power supply Ground fault outside Operates Does not operate 400ms
Grounding
(R) Output
of a substation

Fig. 8 Overview of the Test Circuit of the Power Unit (Arc Tester)
When a ground fault occurs within the substation, the ground
fault protective relay has to make immediate operation output.
5.4 Test Results of the Power Supply Unit Accordingly, we set the time at 15 ms, considering the time
Fig. 9 shows an example of the function test results for the power required to avoid unnecessary operation due to AC ground faults or
unit. As shown there, a constant output voltage (10V) was achieved instantaneous noise.
in relation to unstable input voltage with arcing. On the other hand, we set the operating time for faults outside of
This result shows some temporary drops of the 10V output; the substation at 400 ms considering the above-mentioned detection
however, this is because largely fluctuating arc voltage lowers the time of 50F to identify the damaged line and minimize transport
input voltage to less than 200V. This is correct operation according disruption.
to specification. Fig. 10 shows the appearance of the ground fault protective relay
using no auxiliary energizing source. The structure includes two
units on the attachment base and terminal boards at the bottom.
Table 4 shows the approximate size and weight of the relay.

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Table 4 Size and Weight of the Ground Fault Protective Relay Since the input voltage to the relay in this test was the power
That Uses No Auxiliary Energizing Source supply voltage minus the arc voltage, a voltage that was almost the
Length Width Depth Weight same as the power supply voltage (1,500V) was input just after
beginning the test, and establishment of the 10V output voltage and
530 mm 700 mm 350 mm 19.5 kg
monitoring of the P element started. Input voltage fluctuation was
observed because of arcing, but confirmed that the output voltage
remained stable and within specification operating time (voltage
Ground fault protective relay that uses no auxiliary energizing source monitoring time in ground faults outside of a substation: 400 ms).
Power supply unit Detection/logic unit
We also confirmed that the output voltage of the relay after the
operation output remained stable in relation to the largely fluctuating
input voltage.
Fig. 12 is the magnification of the rise of the power in the test
shown in Fig. 11. Considering the operating time 15 ms in ground
faults within a substation, the response time until reaching 90% of
Terminal board
maximum output is approx. 1.0 ms, which is acceptable.
We secured approx. 1.7 ms response time with 200V input voltage
(minimum voltage to establish 10V output voltage) and approx. 1.0
Fig. 10 Appearance of the Ground Fault Protective Relay
ms response time with 400V input voltage that is the minimum tap
That Uses No Auxiliary Energizing Source
voltage for operation output, the same as in the test with 1,500V
input voltage.
6.2 In-Factory Test of the Ground Fault Protective Relay
That Uses No Auxiliary Energizing Source
To check the basic performance of the developed relay, we carried out Voltage input to the relay

the following in-factory tests other than the test items conducted for

Output voltage (V)

the power unit, achieving test results that specifications are met. Output voltage
Voltage (V)

(1) Measurement of minimum operating voltage: Measurement of

the minimum operating voltage for each set voltage
(2) Measurement of operating time: Measurement of the operating
time from reaching the set voltage to operation output
(3) Measurement of current consumption: Check of relay running at
Time (ms)
the power unit allowable current of 10mA or less Power supply operation starting point

Fig. 12 Response Time of the Power Unit

6.3 Performance Test of the Ground Fault Protective Relay
That Uses No Auxiliary Energizing Source Fig. 13 shows an example of the performance test results in ground
As conducted in the performance test of the power unit, we carried faults within the substation (P element setting value of 400V, B
out a performance test of the developed relay using a pantograph element setting value of 30V).
contact strip elevator.
Fig. 11 shows an example of the performance test results for a Contact strip side voltage

ground fault outside of the substation (P element setting value of

Contact point/Output voltage (V)

600V). Contact wire

side voltage
Voltage (V)

Output voltage
10V
P element setting value: 400V
Contact strip side voltage Voltage to establish 10V output voltage (200V)
Contact point/Output voltage (V)

Voltage input to the relay

(arc voltage)
Operation output
Contact wire side voltage Output voltage Monitoring time approx. 15ms
(voltage input to the relay) 10V
Voltage (V)

Time (ms)

P element setting value: 600V

Fig. 13 Performance Test Results
Fluctuation of voltage input
to the relay (arc voltage)
*Contact strip side voltage −
(Ground Fault within the Substation)
Contact wire side voltage

In this test, we specified the voltage between the contact strip and
Monitoring time Operation output
approx. 400ms the contact wire (arc voltage) as the input voltage to the relay and
Time (ms) checked both of P element and B element at the same input voltage
due to the limitation of the test circuit. Just after starting the test,
Fig. 11 Performance Test Results
(Ground Fault Outside of the Substation) no arc was generated; however, upon lowering the contact strip, arc
occurred. The longer the arc length was, the higher the input voltage

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(arc voltage) became. At the point when the input voltage reached 7.2 Field Test Result
200V, constant 10V output was established. At the point when the Fig. 15 indicates an example of the measurement results in the field
arc length extended to exceed the 400V setting value, monitoring test.
of P element started (B element already being monitored). We
confirmed that the voltage monitoring time was 15 ms for detecting
a ground fault within the substation; that is, the output was made

Voltage between grounding mat and rails (V)

Voltage between grounding mat and rails (V)

Output voltage
within the specification operating time also in ground faults in the
substation.

Output voltage (V)

These performance test results proved stability of the output
voltage in relation to fluctuating input voltage, and that the operation Voltage between grounding mat and rails
(input voltage)
output of the developed relay was achieved according to the set
voltage and time as well.
Voltage between grounding mat
and standard grounding

7
Time (s)
Field Test
Fig. 15 Example of the Field Test Measurement Results
As we confirmed that the target performance level was achieved in
the performance test in the large current test building and in the The measurement results show that the output voltage immediately
factory, we carried out a field test to check durability and unnecessary rose according to a sharp change in voltage between the grounding
operation due to factors such as noise. mat and the rails (grounding mat side as negative), reached a constant
value, and then decreased as the input voltage decreased.
7.1 Overview of the Field Test Circuit The voltage between the grounding mat and the rails remained
As shown in Fig. 14, the input voltage to the developed relay in almost the same during the above-mentioned change.
the field test was supplied in a parallel connection from the input We are currently continuing to take measurements. The number
terminals of an existing 64PB. of data instances that was obtained in the measurement for approx.
a month under the trigger conditions was 11 including the data of
Fig. 15. So far, we have observed no event where the developed relay
has made unnecessary operation due to a sharp change of the input
voltage less than the setting value.

Measurement device
Existing 64PB
8 Conclusion

With an aim of improving reliability of the ground fault protective

function, we developed a ground fault protective relay that uses
no external auxiliary energizing source (DC 110V). An important
success was that we could achieve stable output of the power unit in
relation to unstable input voltage with arcing, the original issue.
We are planning to continue field tests, and to consider building a
highly reliable feeding protection system with an aim of introducing
Ground fault protective relay that
uses no auxiliary energizing source the developed ground fault protective relay that uses no auxiliary
energizing source.

Fig. 14 Overview of the Placement of Devices in the Field Test

Reference:
1) Hitoshi Hayashiya: Arc Phenomena Between the Contact Wire
Measurement was set to record the data when either of the and the Pantograph, p. 16, Japan Railway Engineer’s Association,
following trigger conditions was met. May 2007
(1) 150V or higher voltage between the grounding mat and the rails
(setting value 500V)
(2) Operation of the output contact points of P element and B
element

60 JR EAST Technical Review-No.13