KEHUI T-305E User manual

T-305E High Voltage Surge Generator
User Manual
Kehui International Ltd.
2 Centrus, Mead Lane, Hertford
Hertfordshire, SG13 7GX
United Kingdom
Phone: [phone]
Fax: [phone]
Website: http://kehui.com

T-305E User Manual Version 3.5 | 2
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.
This product is a professional instrument specially designed for power cable faults. Please do not use
it for any other purpose. The company assumes no responsibility or loss if it is used for other
purposes.
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. When product improvement or technical changes occur, you can check
the information through Kehui International Ltd. website http://www.kehui.com.
Disclaimer: Every effort has been made to make this material complete, accurate, and up-to-date. In
addition, changes are periodically added to the information herein; these changes will be
incorporated into new editions of the publication. Kehui International Ltd reserves the right to make
improvements and/or changes to the product(s) and/or the program(s) described in this document
without notice, and shall not be responsible for any damages, including but not limited to
consequential damages, caused by reliance on the material presented, including but not limited to
typographical errors.
NOTE: Windows is a registered trademark of Microsoft.
Revision history:
Data version
Revision date
Revision reason
Person
3.0
2019.05.01
New block diagram and front panel added,
final edit
TonYip/DiaKib
3.1
2019.05.01
New block diagram P8
DiaKib
3.2
2020.02.10
Clarified grounding and T-H200 operation
BilKib
3.3
2021.03.17
Updated technical data, more detail on 2048J
version
BilKib
3.4
2021.04.10
Replacement of diagrams with photographs.
Page numbering & Order codes
BilKib/DiaKib
3.5
2021.07.16
Layout change and additional instructions
following customer feedback
BilKib
Document number: T305E_UM_V3.5_EN

T-305E User Manual Version 3.5 | 3
Foreword
Thank you for purchasing the new product of Kehui - T-305E, the high voltage surge
generator (hereinafter referred to as T-305E)
The T-305E is a high-performance high voltage surge generator with a maximum output
voltage of 32kV and with versions providing a maximum surge energy of 1024J or 2048J. It is
used for pre-location and pinpointing of high impedance and intermittent flashing faults of
underground power cables.
The T-305E provides either DC or single-shot high voltage surge voltage signals to the faulty
cable to break down the fault for pre-location purpose. It works in conjunction with Kehui’s
T-906, cable fault locator, to pre-locate cable faults. T-305E supports the Secondary/
Multiple Impulse Methods (SIM/MIM) and the Impulse Current Method (ICM) for fault pre-
location.
T-305E works in conjunction with the T-506 for cable fault pinpointing. It provides cyclic
impulses to the faulty cable to periodically break down high impedance and flashing faults.
A magnetic field and an acoustic signal are produced during this process. The signals are
used by the T-506 to trace and to pinpoint the fault by the magnetic field and sound
coincidence method. The unit can also be used as a DC power source for the T-H200 sheath
fault locator.
Kehui constantly improves 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.

T-305E User Manual Version 3.5 | 4
Table of Contents
1. SAFETY INSTRUCTIONS ..............................................................................................................5
2. PRODUCT OVERVIEW..................................................................................................................6
2.1 Product features........................................................................................................................6
2.2 Main use and scope of application ..............................................................................................6
2.3 Product nomenclature ...............................................................................................................6
2.4 Environmental conditions...........................................................................................................6
2.5 Standard Configuration ..............................................................................................................6
2.6 Technical Data Sheet..................................................................................................................7
3. WORKING PRINCIPLE...................................................................................................................8
3.1 Basic Operation .........................................................................................................................8
3.2 DC operation .............................................................................................................................9
3.3 Surge operation .........................................................................................................................9
3.4 Low-voltage cable break-down .................................................................................................10
4. EQUIPMENT CONSTRUCTION...................................................................................................11
4.1 User interface Description ........................................................................................................11
4.2 Rear Panel Description .............................................................................................................13
4.3 Side Panel Description..............................................................................................................14
5. GETTING STARTED ....................................................................................................................15
5.1 Using the discharge rod............................................................................................................15
5.2 Wiring connection ...................................................................................................................15
5.3 Modes of operation .................................................................................................................16
6. FAULT PRE-LOCATION...............................................................................................................17
6.1 DC flashover method ...............................................................................................................17
6.2 Impulse flashover method ........................................................................................................18
6.3 Impulse Current Method (ICM) Testing......................................................................................18
6.4 Secondary/Multiple Impulse Method (SIM/MIM) .......................................................................19
7. DC VOLTAGE WITHSTAND TEST ..............................................................................................19
7.1 Cable Connection.....................................................................................................................19
7.2 Performing the Test .................................................................................................................19
7.3 Power off the T-305E ...............................................................................................................20
8. PINPOINTING FAULTS USING THE CYCLIC MODE .................................................................20
9. SHEATH FAULT LOCATION USING THE KEHUI T-H200..........................................................22
10. SHUT-DOWN PROCEDURE.....................................................................................................23
11. MAINTENANCE AND TROUBLESHOOTING...........................................................................23
12. PACKING LIST - T-305E PACKING LIST..................................................................................24

T-305E User Manual Version 3.5 | 5
1. Safety Instructions
Safety Note:
This user manual is the basic commissioning and on-site operation guide for
the T-305E. All operators who will use the T-305E should read the entire
contents of this manual in advance. The manufacturer of this product is not
responsible for any 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:
Please be sure to use Kehui’s spare parts 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]

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2. Product Overview
2.1 Product features
The product has the following characteristics:
1. Three modes of operation: DC, pulse or periodic.
2. Different capacitor bank connection to provide different capacitance by a switch
operation. The energy of the surge is directly proportional to the capacitance value.
3. Interlocking features prevent the equipment from HV operation if the ground is not
securely connected.
4. Automatic discharge facility to remove the charges for the equipment and the cable’s
capacitance after test.
2.2 Main use and scope of application
T-305E is used together with Kehui’s power cable fault locator T-906 and pinpointer T-506, to pre-locate
and to pinpoint underground power cable faults
The equipment consists of voltage conversion and rectification to produce high DC voltage for the
test. Interlocking and safety features ensure safe and reliable operation of the equipment during test.
2.3 Product nomenclature
Product model naming method:
T–3 05 E
Enhancement
Design Number
High voltage surge generator
Cable Test Equipment
2.4 Environmental conditions
1. Working environment temperature: -10°C to 40°C
2. Working environment humidity: 20-90% RH at 25 °C
3. Storage environment temperature: -10°C to 60°C
4. Atmospheric pressure: 86 to 016kPa
2.5 Standard Configuration
1. T-305E instrument
2. Cable for triggering and signalling
3. Earthing cables
4. A user manual

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2.6 Technical Data Sheet
Technical Parameters
Parameter Value
Output Voltage
0-32kV, 0-16kV, 0-8kV, Adjustable negative DC
DC Voltage
0-32kV/25mA negative polarity
Rated capacitance for
1024J version
2μf (when output voltage is from 0 to 32kV)
8μf (when output voltage is from 0 to 16kV)
32μf (when output voltage is from 0 to 8kV)
Rated capacitance for
2048J version
4μf (when output voltage is from 0 to 32kV)
16μf (when output voltage is from 0 to 16kV)
64μf (when output voltage is from 0 to 8kV)
Impulse energy
1024J: (32kV/2μF, 16kV/8μF, 8kV/32μF)
2048J: (32kV/4μF, 16kV/16μF, 8kV/64μF)
Operating mode
DC / Pulse / Cyclic
Testing method
SIM(MIM) / ICM
Discharge period
4 - 15s adjustable continuously when in Cyclic mode
Discharge device
Built-in
Working voltage
220/240Vac10% (110V through step-up transformer)
Mains Frequency
50/60Hz20%
Maximum Power
consumption
1500W
Dimensions
1024J Version: 500x400x960mm
2048J Version: 500x400x1100mm
Weight
75kg for standard (1024J) version
120kg for 2048J version
HV Cable length
3.6m
Ground cable length
4m
Working ground cable
1.1m
Discharge rod cable
2m
Power cable
1.8m
Operating temperature
-10oC to +50oC
Storage temperature
-40oC to +60oC
Ingress Protection
IP21

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3. Working principle
3.1 Basic Operation
At its simplest level the surge generator can be considered to be a capacitor C which is
charged to a selectable voltage (via the transformer) and discharged into the cable through a
contactor S1. The value of the capacitor and the voltage can be changed to optimise the
surge to break down the fault.
The equipment has an internal safety discharge feature. When the equipment is powered
off, the selected capacitors and the cables will be connected to earth/ground through the
safety facility. This works by closing the switch S2 which allows the charge stored in the cable
capacitance and the surge generator capacitor to be safely “dumped” through a resister. A
simplified scheme is shown in figure 3.1. The switch S1 can be controlled by a timer to give
periodic surges required for pinpointing.
Note: References to earth/earthing and ground/grounding are used throughout and are
interchangeable.
Figure 3.1 Surge Generator schematic diagram

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The design of a practical surge generator is more complicated as can be seen in the block
diagram Figure 3.2 for the T-305E.
3.2 DC operation
The surge generator can be used as a DC source by closing switch S1 and applying the
rectified voltage signal directly to the cable. In this way the device may be used to check the
voltage withstand of the cable.
If a fault on the cable breaks down under this voltage, it sets up a travelling wave which
reflects between the fault and the surge generator which can be measured on a suitable
instrument (e.g., The Kehui T-906) through an inductive coupler on the earth lead. The
distance to the fault can be calculated from the time between the voltage peaks on the
resultant waveform and knowledge of the velocity of propagation of the surge.
DC mode can also be used to power a sheath fault locator, such as the Kehui T-H200. Using
the surge generator for this application makes it unnecessary to use a separate power
source such as the Kehui T-100C. Further details can be found in Section 5.
3.3 Surge operation
If the fault cannot be broken down by simply raising the voltage, it will be necessary to send
a surge of energy in to the cable. This is achieved by charging capacitor C to the required
voltage and discharging it into the suspected cable core through switch S1.
The surge of energy in the cable will be reflected from the far end of the cable, such that the
fault is subjected to a voltage approaching twice the value injected (e.g., a surge at 32kV
setting will subject the fault up to 64kV).
The ability to break down the fault is not just a function of the voltage; it is also dependent
on the available energy which is a function of capacitance where the energy in Joules is
equal to ½ CV2where C is in µF and V in kV.
Figure 3.2 T-305 Block diagram

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The stored energy is discharged into the cable with a steep-fronted, high energy surge.
Examples of these waveforms are shown in Figure 3.3.
Figure 3.3. Surge characteristics
This is a series of curves with axes; V (kV) and t (µs). The black line represents a typical fault
characteristic showing that it will not break down instantaneously.
It is a common misconception that the ability of a surge to break down the fault is solely
dependent on the magnitude of its voltage. Figure 3.3 shows that this is not always the case.
If the green 15kV (4µF) curve is considered, it only cuts the fault characteristic after 6 µs,
when it is past its peak. Meanwhile with twice the voltage but a much lower capacitance,
the blue 30kV curve fails to cut the fault characteristic at all and does not result in a
breakdown. Increasing the capacitance by a factor of two, as shown in the red curve causes a
breakdown after around 4µs. The increase in capacitance serves to increase the energy
delivered in the surge, allowing the breakdown to be achieved at a lower voltage, which may
be the difference between a successful and unsuccessful test.
A further benefit of increasing the capacitance is that the extra energy should result in a
louder sound and more vibration at the fault point which will enhance the pinpointing
process.
The T-305E is available in versions with either 1024J output or 2048J, the disadvantage of
the higher value being an increase in the surge generator’s size and weight.
3.4 Low-voltage cable break-down
The term “low voltage cable” refers to cables rated below 400V and hence, the insulation
rating is also low. In order to protect the healthy sections of the cable, the operator should
be careful to ensure the discharge voltage does not exceed 5kV. If it is difficult to break-
down the fault point at this level, it is better to increase the capacitor value. Typically, 5kV
with 10µF should be sufficient to break-down the fault.