KEHUI T-710 User manual

T-710Intelligent Cable Identifier
User Manual
Kehui International Ltd.
2 Centrus, Mead Lane, Hertford
Hertfordshire, SG13 7GX
United Kingdom
Phone: [phone]
Fax: [phone]
Website: http://kehui.com

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Legal Notices
The copyright of this material belongs to Kehui International Ltd. No company or individual
may extract, copy or translate in any way without the written permission of the copyright
owner.
Copyright infringement will be investigated.
This product complies with the design requirements for environmental protection and
personal safety. It is a professional instrument specially designed for power cable
identification and should not be used for any other purpose. The company assumes no
responsibility or loss if it is used incorrectly.
The safety regulations in this user manual should be strictly adhered to.
The storage, use and disposal of the product should be in accordance with the product
manual, relevant contracts or relevant laws and regulations.
As part of Kehui’s continual product development this product is subject to design or
technical changes without prior notice.
Revision history
Data version
Revision date
Revision reason
Person
Version 1.0
December 2020
First issue
D Kibart / W Kibart
Document number: T-710_UM_EN_V1.0

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Foreword
Thank you for purchasing the T-710 intelligent cable identification device.
The T-710 is a light-weight, high power device for accurately identifying a specific cable
from a group of adjacent cables and is a complementary product to the Kehui range of
cable fault location equipment.
In order to ensure that you use the instrument to full advantage, always read the
instructions carefully before using.
Kehui is constantly improving its products, and the individual instruments provided may
differ from the instructions in this manual without prior notice. We are always at your
service if you have any queries or should you require further information.
Please do not attempt to repair or adapt the device, as this will invalidate the warranty. If
you encounter any problem with it contact us on: inf[email protected]m

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Table of Contents
1. SAFETY INSTRUCTIONS .....................................................................................5
2. GENERAL DESCRIPTION.....................................................................................6
2.1 GENERAL ...........................................................................................................6
2.2 FEATURES..........................................................................................................6
2.3 SPECIFICATION..................................................................................................7
2.4 DEVICE COMPOSITION AND ACCESSORIES.......................................................8
3. SIGNAL TRANSMISSION METHODS...................................................................9
3.1 INTRODUCTION TO THE TWO OPERATING METHODS .....................................9
3.2 WIRING AND OPERATION FOR DIRECT CONNECTION....................................10
3.3 WIRING AND OPERATION OF CLAMP COUPLING METHOD ...........................12
4. CONNECTION MODES FOR CABLE IDENTIFICATION.......................................14
4.1 OUT OF SERVICE CABLE WIRING METHOD.....................................................15
4.2 LIVE CABLE WRING METHOD..........................................................................18
4.3 TRANSMISSION FREQUENCY SELECTION IN CABLE DETECTION.....................19
5. SMART CABLE IDENTIFICATION ......................................................................20
5.1 SELECTION OF SIGNAL TRANSMISSION METHOD...........................................20
5.2 RECEIVER FLEXIBLE SENSOR CONNECTION.....................................................20
5.3 INTRODUCTION TO THE RECEIVER INTERFACE...............................................20
5.4 CALIBRATION...................................................................................................21
5.5 CABLE IDENTIFICATION...................................................................................22
6. POWER FREQUENCY CURRENT MEASUREMENT............................................26
6.1 INTERFACE INTRODUCTION............................................................................26
6.2 POSITION ERROR.............................................................................................26
7. TRANSPORTATION AND STORAGE..................................................................27
7.1 TRANSPORTATION CONSIDERATIONS ............................................................27
7.2 STORAGE CONDITIONS AND PRECAUTIONS...................................................27
8. UNPACKING INSPECTION, MAINTENANCE AND WARRANTY .........................27
8.1 INITIAL CHECKS ...............................................................................................27
8.2 MAINTENANCE................................................................................................27
8.3 WARRANTY......................................................................................................28
8.4 PACKING LIST: .................................................................................................29

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1. Safety Instructions
Safety Note: This user manual is the basic commissioning and on-site operation
guide for the T-710 Intelligent Cable Identifier. Any operator who uses the T-710
should read the entire contents of this manual in advance. The manufacturer of this
product is not responsible for the loss caused by the operator's failure to comply
with the operating procedures of this manual or for violation of the safe working
procedures of the operator.
Meaning of the manual symbols: Important instructions concerning personal safety,
operating procedures, technical safety, etc., are marked with the following symbols:
Symbol
Meaning
Indicates a potential hazard that could result in fatal
or serious injury
Indicates a potential hazard which, if not avoided, may
result in minor personal injury or property damage.
Indicates that it contains important information and
useful guidance for using this product. Failure to heed
this information will result in the test not functioning
properly.
Indicates that this is a useful guideline based on field
practice.
Use of accessories: Kehui’s spare parts must always be used to ensure the safe and
reliable use of this instrument. Using accessories made by other companies will
make any warranty null and void.
Repair and maintenance: This instrument must be repaired and maintained by
Kehui or an agent authorised by Kehui. If you have any questions such as
maintenance, cable fault detection, on-site test consultation, etc., please contact;
[email protected]
Earthing / grounding: In English speaking markets the words earthing and
grounding are synonymous for an electrical connection to the mass of earth. For
simplicity, this manual uses the term earthing throughout.

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2. General Description
2.1 General
T-710 is a high-performance cable identification system, composed of a signal
transmitter T-710T and receiver T-710R. It is used to accurately identify the target
cable among multiple cables. It is suitable for live and uncharged cables, including
three-core cables with armour.
2.2 Features
•High-power, multi-level, adjustable output
•The unique identification of the cable, the result is accurate and reliable
•Automatic impedance matching, and protection
•Two signal output modes: direct output and clamp coupling
•Digital, high-precision sampling and processing, extremely narrow receiving
frequency band and strong anti-interference ability
•Built-in large-capacity lithium-ion battery pack, automatic shutdown on under-
voltage and after long periods on non-operation
•Clear identification of cable
•Lightweight, sturdy housing
•Suppression of power frequency and harmonic interference from adjacent
cables and pipelines.
Fig. 2.1 device appearance

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2.3 Specification
2.3.1 Transmitter
•Output frequency: 640Hz or 1280Hz (Composite frequencies)
•Output power: max 10W in 10 steps with automatic impedance matching
•Output voltage: maximum 150V (peak to peak)
•Overload/short circuit protection
•User interface: 320 x 240 pixels LCD
•Internal battery: Four 18650, 7.4V, 6.8 Ah
•Dimensions 280 x 220 x 90mm
•Weight 2.3Kg
•Operating temperature: -10oC to +40oC
•Relative humidity: 5 –90%
2.3.2 Receiver
•Input mode: Flexible sensor
•Active detection frequency 640Hz, 1280Hz
•Passive detection system frequency 50/60Hz (configurable)
•Current measurement: 1 –1000A ±3% AC
•HMI: 800 x 480 pixels LCD
•Battery: Two 18650, 3.7V 6.8Ah
•Dimensions: 220 x 125 x 55mm
•Weight 0.9kg
•Operating temperature: -10oC to +40oC
•Relative humidity: 5 –90%

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2.4 Device composition and Accessories
2.4.1 Transmitter
① LCD Display
⑥ Output frequency increase
② Keypad
⑦ Output power increase
③ Output port
⑧ Output frequency decrease
④ Charging socket
⑨ Output power decrease
⑤ Reset output
⑩ Power on/off
Figure 2.2 Transmitter overview
2.4.2 Receiver
① Output port
⑤ Power on/off
② LCD display
⑥ Calibration key
③ Charging port
⑦ Output frequency decrease
④ Charging socket
⑧ Output frequency increase
Figure 2.3 Receiver overview

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2.4.3 Receiver LCD display
Figure 2.3 Receiver display
3. Signal Transmission Methods
Before making any contact with electrical cables, ensure that the supply is switched
off and the cable is discharged.
There are two methods for the transmitter to transmit signals to the cable: direct
connection and clamp coupling.
3.1 Introduction to the two operating methods
3.1.1 Direct connection method
Using the direct connection method, the output line of the transmitter is directly
connected to the metal cable, in order to inject the signal.
Compared with other methods, the direct connection method produces the largest
current output and so, if conditions permit, it should be used wherever possible.
3.1.2 Clamp coupling
The clamp coupling method is suitable where the cable is exposed, but the conductor
cannot (or is not allowed to) be touched, and both ends of the cable are earthed.
The advantage of the clamp coupling method for transmitting signals is that it is easy
to use, requires no electrical connection to the cable, does not have any impact on
its normal operation and can reduce induction to other cables; the disadvantage is
that the coupled current is less than in the direct connection method and it requires
both ends of the cable to be well earthed.

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3.2 Wiring and operation for direct connection
Step 1: Insert the 5-pin red plug on the output cable directly into the output socket
of the transmitter.
Figure 3.1 Direct connection cable
Step 2: Disconnect the sheath at both ends of the cable, remove the sheath and
neutral earthing.
Step 3: Attach the red clip to a healthy conductor, and the black clip to the earth
through the earthing rod. At the opposite end of the cable, connect the other end of
the connected conductor with the earthing rod inserted in to the ground.
For the near end it is preferable to use the earthing rod rather than the earth grid
network. At the far end, the earthing rod must be used and should be away from the
earthing network. Otherwise, the flow of current through the earth grid will affect
the results.
Connect the red crocodile clip to the exposed core conductor or sheath of the cable;
the black crocodile clip is connected to the earthing pin that is driven into the ground
(soil). If the cable is not long enough, an extension cable can be used.
Figure 3.2 Directly connected to the cable core
Observe the following points:
•Make sure that all connections are solidly made. If there is any insulating coating or
rust on the joint, clean it before connecting the red crocodile clip.
•In order to ensure the detection effect, the earthing pin should be at least 5m away
from the cable, and the black earthing wire should be as perpendicular to the
pipeline as possible.
•Do not connect the black earth wire to a pipe, or there will be transmission signals
induced in it, which will interfere with the normal detection of the target cable.
•There should be no other cables or pipelines between the earthing pin and the
target cable, otherwise the transmission signal will be induced on them, which will
cause interference.

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•The maximum output voltage of the transmitter is 150V. To prevent electric shock,
do not directly touch the output clamp or target cable when working.
The current flows from the transmitter, through the conductor and the earth at the
far end, then travels back to the transmitter. This connection method induces a
strong signal in the receiver.
A strong signal will flow through a well-isolated conductor, it will not flow in nearby
cables, including those crossing the cable path. It is especially suitable for route
tracing in complex environments. In addition, as the cable is earthed, the signal
voltage flow through it is low and does not interfere with other instruments.
Because there is distributed capacitance between the conductor and earth, the
current will attenuate when it flows from one end to the other, but if it is well
earthed, the leakage current will be very low and can be ignored.
Step 3: After completing the wiring, press and hold the power button (Figure 2.2 ⑩)
to turn on the transmitter. The transmitter automatically detects the cable and
confirms the direct connection mode. In this mode, the voltage of the cable will be
measured first - the screen is shown in Figure 3.3a. If the output cable is not detected,
the screen appears as Figure 3.3b.
If the voltage on the cable exceeds the limit (50V), the voltage detection interface
will display a warning sign (Figure 3.3c), and there will be no output thus protecting
the instrument from damage.
Figure 3.3c Overvoltage warning
Figure 3.3a Direct connection mode cable
voltage measurement
Figure 3.3b Direct connection mode no
cable detected

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If the voltage is normal, the signal will be output automatically after a few seconds,
and the screen in Figure 3.4 will appear:
Figure 3.4 Direct connection output interface
Step 4: Pressing the frequency decrease and increase keys selects the transmission
frequency. At power-on, the default frequency is 1280Hz, but 640Hz can also be
chosen, both are composite frequency signals, which the receiver can track as right
or wrong.
There is no uniform standard for which frequency to choose. It can be selected based
on the following principles and actual detection results.
•Generally, for cables with good earthing, most of the tests can be completed by using
the default value of 1280Hz.
•The lower frequencies (640Hz) can be chosen for long cable tracking. The low-
frequency signal has a long propagation distance and will not easily be induced on to
other cables.
Step 5: Press the output decrease and increase keys to adjust the output signal level
(magnitude), which is divided into 10 levels. The output voltage and current are
displayed in the lower right corner of the screen (Figure 3.4).
The default output power is set to half the maximum power. If the receiver signal is
too weak, increasing the power may help to stabilise the reading. Alternatively, if the
receiver displays excessive signal distortion, the output power needs to be reduced.
If the receiver signal continues to be unstable, the reset output button (Figure 2.2
item ⑤) can be used to reset the device and re-apply the signal.
The disadvantage of this connection method is that it requires the disconnection of
the earthing at both ends of the cable which is complicated, care must be taken to
reinstate them correctly.
3.3 Wiring and operation of clamp coupling method
This is an ideal detection method for the live cables as there is no need to reconnect
the cable, making it very safe for the operator. There is a signal throughout the entire
length of the cable, and no distance limitation.
Both ends of the cable sheath should be earthed as the coupling current will
decrease as earthing resistance increases.
The clamp coupling method can only be used where both ends are earthed and the
sheath is unbroken.

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Step 1: Insert one end of the transmitter accessory connection cable (red 5-pin plugs
at both ends) into the transmitter clamp socket, and the other end into the
transmitter output socket.
Figure 3.5 Clamp cable connection
Step 2: Attach the clamp around an exposed part of the cable, as shown in the
following figure:
Figure 3 6 The clamp method is connected to the pipeline
•Both ends of the cable must be earthed to induce a signal.
•When putting the clamp around the cable, make sure that the jaws are completely
closed, and that there is no foreign matter or rust on the jaws.
Step 3: After completing the wiring, when the transmitter is turned on, it will
automatically detect the connected test line and lock it in the clamp output mode.

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The screen displays as follows:
Figure 3.7 Clamp connection output interface
Step 4: Press the frequency increase and decrease keys to select the transmit
frequency. There are two frequencies to choose from: 1280Hz (The default when the
unit is energised) and 640Hz.
Frequency selection in the clamp coupling method is the same as in the direct
connection method, repeated here for clarity:
There is no uniform standard for which frequency to choose. It can be selected based
on the following principles and actual detection results.
•Generally, for cables with good earthing, most of the tests can be completed
by using the default value of 1280Hz.
•The lower frequencies (640Hz) can be chosen for long cables. The low-
frequency signal has a long propagation distance and will not easily be
induced on to other cables.
Step 5: Press the output increase and decrease keys to adjust the output, which is
divided into 10 levels.
The default output power is set to half the maximum power. If the receiver signal is
too weak, increasing the power may help to stabilise the reading. Alternatively, if the
receiver displays excessive signal distortion, the output power needs to be reduced.
However, the current coupled to the cable through the clamp is much smaller than
the direct connection method and the maximum output level should be used
wherever possible.
If the receiver signal continues to be unstable, the reset output button (Figure 2.2
item ⑤) can be used to reset the device and re-apply the signal.
The clamp coupling method cannot display the voltage and current coupled to the
cable.
4. Connection modes for cable identification
The ability to identify a particular cable is an important aspect of cable maintenance.
Cables are often composed of several core conductors with metal armour. Different
wiring methods produce different electromagnetic fields and require detection
approaches described in the following section.

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4.1 Out of service cable wiring method
For the detection of outage cables, the direct signal transmission method is mainly
used to generate the maximum transmission current.
4.1.1 Core conductor-earth connection
The core conductor-earth connection method is the best wiring method to identify
the out-of-service cable (the uncharged cable that is out of service), which can give
full play to the performance of the instrument and shield interference to the greatest
extent. The specific wiring is shown in the figure below:
Figure 4.1 Core conductor-earth method, wiring diagram
Figure 4.2 Core conductor-earth method principal diagram
Before making any contact with the cable, ensure that it is switched off and fully
discharged.
For this method it is important that the return path, through the connected
conductor and its earth connection, is the only available path for the signal. Hence,
it is necessary to disconnect the earth wires at both ends of the cable’s metal sheath.
For low-voltage cable it will also be necessary to disconnect the neutral wire, if it is
earthed, and the earth wire.
Attach the red crocodile clip of the transmitter to one of the cores, and the black
crocodile clip to an earthing pin driven into the ground. At the opposite end of the
cable, the corresponding core conductor is connected to another earthing pin.
Due to the anti-error tracking function of the instrument; the signal flows through
the well-insulated core conductor and will not flow in adjacent cores. In addition,
because the cable is earthed, the signal voltage is very low, preventing capacitive
coupling to adjacent lines, reducing interference.
Earthing pins should be used as much as possible, rather than using the earth grid.
The remote end must always be earthed using an earthing pin which should be
inserted into the ground as far as possible from the earth grid, otherwise earth
current return may flow on other cables, adversely affecting the measurement.

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The current is injected into the core conductor from the transmitter, enters the earth
at the opposite end of the cable, and finally returns to the transmitter through the
ground. The receiver will sense a strong signal, with clear signal characteristics. The
signal flows through a well-insulated core conductor and will not flow in adjacent
pipes or cables. In addition, because the cable is earthed, the signal voltage is very
low, and making capacitive coupling to adjacent lines unlikely, hence reducing
interference.
Due to the distributed capacitance between the core conductor and the ground, the
current will gradually decrease as the distance increases. However, if the earthing is
good, the capacitive current is very small and can be ignored.
The disadvantage of this method is the need to disconnect the earthing wires at both
ends of the cable, which can be inconvenient.
4.1.2 Sheath-earth connection
The protective layer-earth wiring diagram and principle are as follows.
Figure 4.3 Connection diagram of sheath-earth method
Figure 4.4 Schematic diagram of sheath-earth method
As shown in the figure above, the earth wire to the sheath must be disconnected at
the near end of the cable. For this method it is important that the return path
through the sheath and its remote earth connection is the only available path for the
signal. Hence, for low-voltage cables, it will also be necessary to disconnect the
neutral wire, if it is earthed, and the earth wire.
With this method, the cable sheath at the far end remains earthed. A signal is then
applied between the sheath and an earthing pin inserted in to the ground (Do not
use the earth grid). No connection is made to the cable core. Current is injected into
the sheath from the transmitter, it is conducted along the sheath and enters the earth
at the opposite end of the cable, returning to the transmitter through the ground.
There is no shielding in this connection, so the signal generated in the ground is
strong and the signal characteristics are relatively clear.

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Similarly, due to the existence of distributed capacitance between the sheath and
earth, the signal will gradually attenuate along the cable.
If the insulating layer outside the protective layer is damaged, part of the current will
flow into the ground from this point, causing the current flowing beyond it to
suddenly decrease. The reduction in the current is proportional to the earth
resistance at the fault point. This may affect the use of the current intensity criterion,
which is why this method is not preferred.
4.1.3 Core conductor (phase conductor)-sheath connection
Figure 4.5 Wiring diagram of core conductor-sheath method
Figure 4.6 Schematic diagram of core conductor-sheath method
As shown in Figure 4.5 above, the transmitted signal is connected between one of
the phase cores of the cable and the sheath. The connected core and the sheath at
the far end are short-circuited, with both ends of the sheath earthed.
The signal is injected into the core from the transmitter and returns through both the
shield and the earth. As the shield is composed of continuous metal, the resistance
is very small, however, the earth loop has a large resistance value due to the earthing
resistance at both ends and the earth resistance. As a result, most of the current will
return through the protective layer, with only a small portion of the current returns
through the earth.
Since the core conductor current and the sheath current are flowing in reverse
directions, the effective current which will generate a magnetic field signal is the
difference between the two, with the value being equal to the resistance current
returning through the earth. In addition, due to the mutual inductance between the
core conductor-sheath loop and the sheath-earth loop, electromagnetic induction
can also induce current in the sheath-earth loop.
Therefore, the total effective current is equal to the vector sum of the resistance
current and the induced current of the earth loop (there is a phase difference
between the two). Depending on site conditions, the total effective current may
account for up to ten percent of the total injected current.

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If there are other cables laid in the same path (with their ends in the same place),
the return current will be mainly divided between the sheaths of several cables. For
example, if three cables have the same path, the sheath return current of the three
cables will each account for 1/3 of the total. The effective current in the cable under
test, is in the forward direction, accounting for 2/3 of the injected value. In the
adjacent lines, the current is in the reverse direction, accounting for 1/3 of the
injected value. As shown in Figure 4.7.
Figure 4.7 Diagram showing the effect of the core conductor-
sheath method on parallel cables
The core conductor-sheath method has the advantage of simple wiring and no need
to disconnect the earth wire. The disadvantage is that when multiple cables are laid
in the same path, the signal of each cable is not much different, and it is sometimes
difficult to distinguish only by the signal amplitude; when single-conductor laying,
the effective current is greatly reduced, the signal is weak, and the effective current
contains induced current components, the phase of the induction signal of the target
cable and the adjacent pipeline is the same. When using composite frequency
detection, it may not be possible to exclude adjacent line interference according to
the current direction.
4.2 Live cable wring method
4.2.1 Clamp coupling method
The clamp coupling method provides an effective way of identifying live cables. It
allows safe testing without the need to directly access the live cable. The method
relies on the voltage signal which is present over the entire length of the cable, such
that there is no distance limit.
When applying the clamp coupling method, both ends of the cable sheath must be
properly earthed, otherwise the coupling current will decrease with the increase of
earth resistance. If the two ends are not earthed, or the cable sheath is disconnected,
this method cannot be used.
The clamp coupling method requires the sensor to be clamped around the cable body.
It is suitable for the identification of ordinary three-phase cables. The transmitter
output is connected to the clamp, which is then attached to the cable body (noting
that it should not be attached to the portion of the cable beyond the earth wire). The
clamp is equivalent to a primary winding of a transformer, and the cable sheath to
earth loop is equivalent to a single-turn secondary of the transformer.

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Figure 4.7 Correct, and incorrect, methods of cable clamping
The magnitude of the secondary coupling current is inversely proportional to the
loop resistance, which mainly consists of the earthing resistance at both ends. The
two ends of the cable must be well earthed to facilitate a high coupling current. If
the current is small and it is confirmed that the measurement is being taken from
the target cable, the quality of the earth bond should be checked.
The current induced in the cable through the clamp is relatively small. In order to
improve detection, a larger output level may need to be selected.
The clamp method is not suitable for identifying live, very high voltage single-core
cables. In this case, the power frequency current flowing through the core of the
cable is very high, and the other phases are separate. Hence, there is no three-phase
cancellation effect, as with a three-core cable. The high current in the cable may
cause magnetic saturation of the sensor, so that it fails to measure high-frequency
signals correctly.
4.3 Transmission frequency selection in cable detection
For general cable detection, unless the phase indirect method is adopted, it is
recommended to use the default frequency of 1280 Hz which is selected when the
power is turned on. This relatively low frequency gives a long propagation distance
and it is not easily induced into adjacent cables or pipelines; in addition, the
reception of the receiver at 1280Hz signal is stronger than at 640Hz and it has a
stronger resistance to interference making it easier to distinguish.
If a 1280Hz signal is used for cables longer than 2-3km, there will be greater
attenuation making the signal reception poorer and the phase may also shift.
Therefore, it is recommended to use 640Hz when transmitting signals for the
detection of long-distance cables.
640Hz and 1280Hz are composite frequency signals, allowing the receiver to readily
identify them.

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5. Intelligent Cable Identification
When laying cables for an electric power system, their unique identification is vital to
ensure the safety of personnel and to prevent damage to equipment and plant.
Intelligent recognition using the flexible sensor facilitates clear results with immunity
to interference.
5.1 Selection of signal transmission method
The transmitter must be set to 1280Hz or 640Hz frequency. Generally, using the
default value of 1280Hz will meet most test requirements, with 640Hz being used
for extra-long cables.
For non-operating cables with no voltage present, use the direct connection
method, with the core conductor-earth connection method being preferred; if this
method is not convenient, use the phase conductor-sheath connection method.
The sheath-earth connection method is not recommended.
The clamp coupling method must be used for live cables.
5.2 Receiver flexible sensor connection
Insert the lead of the flexible sensor into the accessory input socket on the
receiver, as shown in the figure below.
Figure 5.1 Flexible sensor connection
5.3 Introduction to the receiver interface
After power on, the receiver automatically recognises the connected accessories
and sets it to sensor receiving mode. The interface is as follows:
Figure 5.2 Receiver interface