A welcome diagnosis: you have untapped reserves of efficiency!

SebaKMT diagnostic methods

for commisioning testing and

condition analysis will increase

the efficiency of your network.

Find out how it works. And what happens next.

Diagnosis is our speciality.

The SebaKMT diagnosis

philosophy

One of the goals of SebaKMT

diagnosis technologies is to

avoid service interruptions

during network operation in

medium voltage, high voltage

and extra high voltage cable

systems. Service interruptions

are primarily caused by dam-

ages to the cable caused by

laying, workmanship failures on

accessories and ageing related

causes on joints, terminations

and cable insulation. The

second goal is to save costs by

effi ciently replace cables based

on their condition.

With SebaKMT diagnostic

systems, all damages and

installation failures can be

detected and corrected in order

to avoid network failures and the

subsequent costs that they

incur. On the one hand, it is

possible to check these factors

before a cable is put into

operation. At this time, all

components can still be easily

reached and the quality of the

new cable system is verifi ed.

On the other hand, permanent

or periodic condition analysis

can identify impending faults

and make it possible to carry

out condition-based mainte-

nance work on the network thus

also preventing interruptions

during operation.

Commissioning testing

Since the insulation of the cable

is assumed to be new when

carrying out a commissioning

testing, the main focus of the

diagnosis lays on the quality of

the cable laying and installation.

For example, sheath fau lts

caused by mechanical damage

during laying or incorrectly

installed joints and terminators

are detected. For commissioning

testing, the SebaKMT partial

discharge diagnosis (PD diagno-

sis) can be deployed. You will

fi nd more detailed information

about commissioning testing on

pages 4 and 5.

Condition-based

maintenance by means

of continuous condition

analysis

With the aid of SebaKMT

diagnosis procedures, aging-

related damage to the insulation

of laid cables can be detected

reliably. Furthermore, an exten-

sive network condition analysis

with SebaKMT cable diagnosis

systems can answer questions

relating to the operational

reliability as well as the quality

and integral residual strength of

the insulation material. In this

way, a meaningful prognosis can

be produced regarding the

future risk of failure.

The PD diagnosis is used to

check accessories and to

localise weak spots in the cable.

It can also be applied for moni-

toring during live network

operation.

The most effi cient way: prevent opera tional breakdowns from arising in the fi rst place.

The Dielectric diagnosis, on

the other hand, is used to check

the quality of cable insulation.

You will fi nd more detailed

information about condition-

based maintenance on pages

6 to 9.

2 3

Offl ine

Offl ineOnline

PD diagnosis

Commissioning test

Online

RVM IRCTan δ

Dielectric diagnosis

Condition analysis

Offl ine

RVM IRCTan δ

Dielectric diagnosis

IRC

PD diagnosis

Commissioning testing with PD dia gnosis.

The “first” step to ef ficient network operation.

Modern commissioning testing.

cable faults shortly after putting

the cable into operation and, as

a consequence, the costs for

the repair which could have

been avoided.

In addition, conventional proce-

dures for commissioning testing

are not able to uncover installa-

tion errors that only “grow” to

become faults in the course of

time. It is a well-known fact that

such errors are accompanied by

partial discharges long before the

component in question fails.

For this reason, commissioning

tests are combined increasingly

with a partial discharge diagnosis

(PD diagnosis) or are completely

replaced by it. By means of

PD diagnosis, all types of

workmanship failures can be

easily detected and pinpointed.

In this way, the functionality of

the network infrastructure is

guaranteed from the first day

of operation onwards and

unplanned failures and repairs

are reduced significantly. The

SebaKMT partial discharge

diagnosis, which goes up to

350 kV, covers almost all

Commissioning testing.

Past and present

The procedure applied for

com missioning testing depends

on the voltage level. Medium-

voltage cables are mainly tested

with 0.1 Hz voltage. Due to

economical reasons, high-volt-

age cables are frequently put

into operation after a soaking

test at Uo for 24 hours. A test

with variable frequency resonant

voltage or attenuated AC voltage

greater than Uo is significantly

more meaningful. However, the

mentioned procedures do not

provide the network operator will

all the relevant information about

the quality of the cable laying

and installation. These gaps in

the information frequently lead to

applications from the lower

medium voltage range to high

and extra high voltages. For indi-

vidual appli cations, SebaKMT

also offers tailor-made and

customized solutions.

Safety and reliability right from the start:

Commissinoing testing with SebaKMT OWTS technology.

An introduction to the OWTS technology is provided on pages 10/11.

On pages 12 to 15, you will find the OWTS product line range.

4 5

Commissioning testing with OWTS HV 150

PD diagnosis is especially suitable for testing the quality of cable laying and installation (pictures ABB)

PD diagnosis

Offline

Commissioning testing

Technologies for syste-

matic condition analysis

In order to produce a meaningful

condition assessment, not only

the state of the cable's insulation

but also local weak points must

be considered. To comply both

dielectric and PD diagnosis

must be used. Logically all

SebaKMT diagnostic methods

are non-destructive. They will

not age the insulation or even

result in a breakdown.

Dielectric diagnosis

The condition of the cable

insulation is infl uenced by

normal aging processes over the

years in operation as well as by

external effects. These include,

Continuous condition analy sis

to guarantee efficient network operation.

Condition-based

maintenance by means of

continuous condition

analysis

Continuous condition analysis

provides your company with all

relevant information about the

actual condition of your network.

A cycle is created consisting of

measurement, analysis and

revolving planning. Based on the

gained knowledge, it has

become possible to deploy the

condition-based-maintenance

strategy.

The facts about the condition of your network.

Information is the basis for

reliable decisions

Expansion and maintenance of

the cable network are signifi cant

cost items in a power utility

company's budget. Accordingly,

knowledge about the current

condition of the network is of

special importance, also in

terms of fi nancial planning

aspects: The more precisely

maintenance work, repairs and

replacement of systems are

planned, the more effi ciently can

the network be operated.

This guarantees strategic,

continuous and therefore

effi cient use of your resources:

– Replacement of cables based

on their condition

– Effective planning of

maintenance work

– Long-term reduction of

unplanned interruptions

among others, moisture pene-

tration as well as operating

loads, both normal and excep-

tional, such as overloads or

overvoltages/surges. The

procedures for dielectric condi-

tion analysis are tuned to the

specifi c physical properties of

paper and XLPE insulation.

Aging effects such as water

trees in XLPE cables or degra-

dation of cellulose in the case

of mass-impregnated cables

can be detected by means of

dielectric diagnosis in the

frequency/time domain. Accor-

dingly, the operational reliability

of cable network can be

assessed with a high degree

of precision with the following

analysis procedures.

6 7

Isothermal relaxation

current analysis - IRC

The IRC analysis is a proven

dielectric procedure which

provides integral details about

the condition of PE/XLPE

insulated cables in terms of

ageing and damage. The

functionality of this procedure

is based on the discharge

current (depolarisation current).

First, the cable is charged with

a voltage of 1 kV and afterwards

the relaxation current (discharge

current) is measured over a

period of 30 minutes.

Transition of an electrical tree on top of a water tree

PD diagnosis Dielectric diagnosis

Offl ine IRC RVMOnline Tan δ

Condition analysis

Tan delta 0.1 Hz dissipation

factor measurement

With the 0.1 Hz dissipation

factor measurement, the tan

delta loss factor is measured

with specified sine wave test

voltages at 0.1 Hz and varying

voltage. The insulation’s ohmic

leakage current is significant for

determining the δ angle between

the ideal capacitive current and

the complex current. In fact the

ohmic current is proportional

with the δ angle, an increase in

ohmic current therefore means a

poorer condition of the cable.

Analysed is the absolute value of

the tan delta as well as the

increase in the tan delta with

respect to the voltage, also

called tip-up or Δ tan δ.

Return voltage measure-

ment (RVM)

RVM measurement is a proven

dielectric procedure in time-do-

main for evalu ating the ageing

condition of paper-insulated

cables. After charging for a

defined period and briefly

discharging the capacity of the

test object, the return voltage

curve is measured and recorded

for two different forming volt-

ages, 1 and 2 kV. The ratio

between the two return voltage

curves gives an outcome about

the condition of the cable. The

RVM diagnosis is carried out

according to the principles of

the return voltage measurement,

which has been in practice for

more then a decade for testing

power transformers.

Do it the easy way: our mea surement procedures.

A neuro-fuzzy software module

is used to evaluate the IRC test

results. This expert-type multi-

stage, intelligent evaluation

software takes into account

specific design features of the

cable under test and catego-

rises the condition of the tested

cable based on a reference

database. Included in the

evaluation is an estimated

residual strength prognosis.

Online and offline partial

discharge measurement

procedures

Along with dielectric diagnosis,

PD measurement is also neces-

sary for comprehensive evalu-

ation of the condition of the

network. During commissioning

testing, it is important to evalu-

ate the quality of the installation

and cable laying; for condition-

based maintenance, the focus is

on the condition of accessories

that have aged during operation

and the insulation of the cable.

For example, by means of offline

PD measurement, the degree to

which paper insulation has dried

out can be analysed or external

damage caused by construction

work can be located. Compli-

mentary to this, online PD

monitoring offers a cable

monitoring feature thus making

it possible to preselect cables

with PD faults. Finally, the offline

PD measurement procedures are

used for pinpointing the faults.

Monitoring with the online

PD measurement procedure

The major advantage of online

monitoring is that in most cases it

is not necessary to disconnect

the cable. This reduces the

organisational effort. In addition,

the influence of the load on the

PD-activity can be recognized.

The procedure is therefore ideally

suited for monitoring trends e.g.

in industrial networks.

Local diagnosis with the

offline PD measurement

procedure

Offline PD measurement is

suitable for locating the PD

pulses, e.g. after measuring

critical PD values with the online

PD measurement procedure.

Without being affected by

interference levels from online

operation, this proven technol-

ogy makes it possible to locate

partial discharges with a high

degree of sensitivity and preci-

sion. When doing so, it is

possible to determine the PD

inception voltage PDIV as well

as the PD extinction voltage

PDEV. Together with the level of

partial discharge, the PDIV is

one of the key indicators of

whether accessories or cable

(-parts) needs to be replaced.

Different procedures, one goal: efficiency.

8 9

• OWTS technology pages 10/11

• OWTS product introduction pages 12 to 15

• CDS page 16

• VLF tan delta page 17

• LPD monitor pages 18/19

PD diagnosis Dielectric diagnosis

Offline IRC RVMOnline Tan δ

Condition analysis

Two partners – a unique

technology

SebaKMT and Seitz Instruments

offer the Oscillating Wave Test

System (OWTS) technology –

jointly and worldwide. The

advantage of this technology is

that OWTS equipment can be

used for commissioning testing

as well as for systematic condi-

tion analysis as part of a condi-

tion-based maintenance strat-

egy. This reduces costs for

investment in different

technologies.

One system –

many benefits

With help from the OWTS

technology age-related weak

spots and damages to the cable

e.g. caused by construction

works, can easily be detected

and located. Moreover the

intregrated tan delta procedure

provides a very good assess-

ment of the condition of the

insulation medium. The OWTS

technology also provides

benefits with the evaluation of

high-voltage cables: The

majority of the laid HV cables

are over 30 years old and are

paper-insulated cables such

as internal and external gas

pressurized or oil pressurized

cables.

Using OWTS technology,

these cables can be not only

examined for local faults but

also analysed integrally with the

integrated tan delta procedure.

OWTS – reliable, simple,

non-destructive diagnosis

The functionality of the OWTS

technology is based on a

resonant circuit between the

cable capacity and the choke of

the OWTS system. The test

object is charged to the desired

voltage within a few seconds

and is then discharged via a

high voltage switch and a choke.

In this way, an oscillating voltage

is created whose oscillating

frequency depends on the

OWTS technology. Ideal for commissioning testing

and systematic condition analysis.

A unique technology.

inductance of the choke and the

capacity of the test object. The

oscillating voltage (DAC voltage,

damped AC) is an internationally

accepted standardised test

voltage. Depending on the

length of the cable to be tested

and its length-related capacity,

an oscillating voltage is pro-

duced with a frequency that

comes close to the operating

frequency. As opposed to the

methods based on 0.1 Hz, this

allows PD faults to be detected

under network conditions and

the PD parameters, such as

the partial discharge inception

voltage (PDIV), to be compared.

The test level also remains within

the range of the operating

voltage thus making non-

destructive testing possible.

The partial discharge measuring

circuit is calibrated according to

IEC 60270. The PDIV is deter-

mined by increasing the test

voltage gradually. The PDEV

(Partial Discharge Extinctio

Voltage) can be determined

clearly by means of the attenu-

ated voltage. PD faults are

located by means of the soft-

ware, based on the so called

TDR principle (Time-Domain-

Reflectometry). In semi or fully

automatic mode the location of

the partial discharges is calcu-

lated of the recorded and saved

data. The result being is a

PD-mapping as shown below on

the right hand side, where the

x-axes shows the cable length

and the y-axes the PD-height.

1 0 1 1

While measuring, the oscillation of the voltage produced by the test equipment can be seen clearly.

The analysis shows the partial discharges for all 3 phases of the system. PD-activity occurs in several joints spreaded over a acble length of 6500 m.

• Information about OWTS

systems on pages 12 to 15

PD diagnosis

Offline Online

The OWTS series. Compact and perfectly

tailored to your needs.

Long line?

No problem!

Some of the outstanding

advantages of the SebaKMT

OWTS systems are their com-

pact form, low weight and

exceptionally high test capaci-

ties. Cables of 20 kilometres or

more can be easily tested, in

accordance, with the interna-

tional standards. As opposed to

a simple 24-hour test at U0, the

OWTS technology allows testing

and diagnosis with higher

voltages. Meaning that also

endangering workmanship

failures with an inception voltage

above U0 can be detected and

located. With the OWTS M

series (28 and 60 kV) and OWTS

HV series (150, 250 and 350 kV),

the SebaKMT OWTS product

range covers almost the entire

spectrum of supply network

voltages with a non-destructive

partial discharge diagnosis.

OWTS M

The most striking characteristic

of the OWTS M concept is its

compact design. It is based on a

single fully integrated HV part

which includes all functions and

components of the HV and PD

diagnosis technology. Operation

and control as well as evaluation

of the data is carried out easily

with a standard notebook

connected to the high-voltage

unit via WLAN or Ethernet.

OWTS M 28

The voltage of this portable

system is dimensioned for

testing cables with nominal

voltages up to 20 kV up to

1.7 U0. PD diagnosis up to

1.7 U0 is suffi cient because, in

case of a phase-to-ground

failure, the maximum voltage in

the other two phases will be the

phase-to-phase voltage.

Small machines, big performance!

OWTS M 60

The next largest system is the

OWTS M 60 which can test

cables up to a rated voltage of

45 kV at 1.7 U0. The OWTS M

60 is especially suitable for

commissioning testing on very

long cables, e.g. offshore or

onshore wind park cables.

OWTS HV

For voltage testing or PD

diagnosis on high-voltage

cables, SebaKMT offers the

OWTS HV 150, 250 and 350 kV.

These systems cover all cables

ranging from the lower high

voltage range up to the extra

high voltage range up to 380 kV.

SebaKMT also develops

customized solutions which

are perfectly tailored to your

individual needs.

OWTS Skip PD

connection set

Since a PD-free connection on

the test object is essential for

sensitive PD measurements,

SebaKMT has developed the

OWTS connection set. This

connection set allows the user

to make a PD free connection

to the test object for the majority

of the available switchgear

systems. A reliable connection

and sensitive PD measurements

are thereby guaranteed.

1 2 1 3

OWTS M 60 OWTS M 28

OWTS connection setOWTS connection set

Wind park

PD diagnosis

Offl ine Online

Machines for the PD pinpointing.

PD LOC

It goes without saying that

locating partial discharge also

includes the possibility of

pinpointing faults. The SebaKMT

PD LOC takes care of this

perfectly.

The PD location system consists

of a coupling unit which induces

pulses similar to partial discharge

in the cable.

The right equipment for out standing results.

These pulses are received by a

specially adapted refl ectometer

at the beginning of the cable and

located in the same way as with

OWTS fault location. Since the

OWTS and the refl ectometer

being used work with identical

parameters, the result is very

precise and allows the position

of the partial discharge point that

was previously located to be

confi rmed.

PD detector

With TE-PDS SebaKMT offers

an easy to use handheld device

for locating PD in terminations or

in joints. For example transition

joints in substations can easily

be checked for PD-activity.

1 4 1 5

TE PDS

pulses similar to partial discharge

in the cable.

was previously located to be

confi rmed.

PD LOC

Performance data of the OWTS range at a glance

System voltage UL U0 OWTS M 28 OWTS M 60 OWTS HV 150 OWTS HV 250 OWTS HV 350

[kVRMS] [kVRMS] U0 [kVRMS] U0 [kVRMS] U0 [kVRMS] U0 [kVRMS] U0 [kVRMS]

6 kV … 22 kV 3.5 kV … 12.7 kV 5.7 … 1.6

22 kV … 50 kV 12.7 kV … 28.9 kV 1.6 … 0.7 3.3 … 1.5

50 kV 29 kV 0.7 1.5 3.7

66 kV 38 kV 1.1 2.8

110 kV 63 kV 1.7 2.8

132 kV 76 kV 1.4 2.3

150 kV 87 kV 1.2 2 2.8

220 kV 127 kV 1.4 1.9

330 kV 191 kV 1.3

380 kV 219 kV 1.1

OWTS HV 350

PD diagnosis

Offl ine Online

The portable CDS system

The portable CDS system is a

universal system for dielectric

diagnostics of PE/XLPE insu-

lated as well as mass-impreg-

nated cables. The system

includes the IRC and RVM

measuring processes.

Tan delta measurement

SebaKMT also offers a tan delta

test attachment to complement

the CDS system.

The attachment can be used in

combination with 0.1 Hz VLF

sine voltage sources for dielec-

tric diagnosis in the frequency

domain. The tan delta test

attachment achieves very

accurate measurements

because it measures at the

high voltage potential and the

measuring head is positioned

very close to the test object.

In this way, external influences

caused by e.g. sheath faults or

multiple grounded situations can

be excluded.

More precise measurements

can be achieved with the

optional leakage current correc-

tion feature. This corrects the

leakage current which could

flow along the terminations due

to contamination or moisture

and or moisture and can have

a significant influence on the

measured tan delta value.

Dielectric diagnosis made by SebaKMT.

1 6 1 7

Non-destructive, integral

diagnosis technology.

Cable diagnosis with CDS is

100 % non-destructive because

the measurement voltage for the

diagnosis is only a fraction of the

operating voltage of the cable.

Furthermore, the CDS is a very

light and portable system. The

test-time is reduced to a mini-

mum, since all three phases are

measured at once. Measure-

ment results are evaluated

automatically and shown clearly

in a log which is produced

automatically.

CDS

The tan delta test attachment integrated in a diagnosis vehicle.

Dielectric diagnosis

IRC RVM Tan δ

Monitoring: Systematic moni toring results in

a reliable diagnosis.

LPD Monitor

With LPD Monitor (Live Partial

Discharge Monitor), SebaKMT

offers an easy to use online PD

monitor solution for monitoring

MV cables and plants, on a

temporary or continuous basis,

up to a nominal voltage of 66 kV.

With its 16 input channels, the

lightweight LPD Monitor is an

ideal,portable system for a fast

check of critical PD within cables

or their accessories.

Mobile and simple diagnosis.

Even a quick “look and see” test

can provide useful information

about the condition of the cable

as a basis for planning any

required maintenance work,

such as a comprehensive offl ine

PD diagnosis.

The gathered data is analysed

automatically by the integrated

software. PD pulses are segre-

gated from noise and catego-

rised in local PD meaning PD in

the MV plant or near termination

and partial discharges in the

cable. The results are subse-

quently compared with the

integrated knowledge database

and then assigned to one of four

possible assessment categories.

PD activity rated as “critical” can

generate an alarm message.

1 8 1 9

The above case study demonstrates the extra value of online PD monitoring on PILC cables. The upper graph shows the load current and the lower graph shows the PD activity, both are plotted against time. Partial discharges occur when the cable is cold, unloaded condition. When the cable is warm, loaded condition, the PD-activity disappears. The simple explanation for this phenomenon is that the insulation medium mass-impregnation/oil becomes fl uid when it warms up, when voids occur the will be directly fi lled with oil again, thus partial discharge activity is pre-vented; when cold, on the other hand, it does not fulfi l its function perfectly thus allowing damage to the cable due to partial discharges.

With its 16 input channels, the

lightweight LPD Monitor is an

ideal,portable system for a fast

check of critical PD within cables

quently compared with the

integrated knowledge database

and then assigned to one of four

possible assessment categories.

PD activity rated as “critical” can

generate an alarm message.

LPD Monitor

PD diagnosis

Offl ine Online

Competence:

We are the world's leading developer and manufacturer of

measurement equipment for diagnosing the condition of

networks and for locating faults. Our market sectors include

electricity supply networks as well as communication and

pipe networks.

Performance:

We concentrate on five areas: network condition analysis, cable

fault location, leak location, sewer TV inspection and line location.

We are thus in the position to offer high performance in each of

these areas.

Availability:

SebaKMT has representatives in 130 countries worldwide with

excellently trained staff and the most modern technology. This

means we have the best service and support network coverage

in the industry. Wherever your international activities may lead

you, we look forward to speaking to you.

SebaKMT

Dr.-Herbert-Iann-Strasse 6

96148 Baunach/Germany

Tel. +49 (0) 95 44 - 6 80

Fax +49 (0) 95 44 - 22 73

sales@sebakmt.com

www.sebakmt.com

Countries with SebaKMT representatives

sebaKMT is the registered trademark of the sebaKMT Group

Dia

gnos

ebro

schü

re_e

ng_2

010_

25