Končar TMS - Bushing monitoring - Az-Teknik€¦ · Rajko Gardijan, dipl. ing. Samir Keitoue, dipl.ing. Head of Transformer Department Head of TMS section [email protected]

Koncar Electrical Engineering Institute Inc.

Fallerovo setaliste 22, Zagreb, Croatia www.koncar-institut.hr

___________________________________________________________________________ Contact: Rajko Gardijan, dipl. ing. Samir Keitoue, dipl.ing.

Head of Transformer Department Head of TMS section [email protected] [email protected]

Končar TMS - Bushing monitoring

Many recent studies have shown that

bushing failure is one of the most common

causes of transformer failure. Thus need for

bushing diagnostic and monitoring system

has risen. Although, the offline diagnostic

gives more accurate and precise insight in

bushing insulation state, it is still not common

practice for substation maintenance to

perform such test very often. Main reason is

that it demands transformer outage, well

trained personnel and expensive equipment.

Koncar TMS bushing monitoring provides

insight in bushing insulation state while

transformer is online. Developing fault inside

bushing now can be detected in very early

stage so proper action can be taken to save

substation equipment and personnel.

Powerful digital signal processor module

enables precise measurement of bushing

leakage current amplitude and phase angle.

By measuring those parameters, relative

dissipation factor change ( tan ) and

relative capacitance change ( 0C C ) can be

estimated.

Key features:

Bushing capacitance and tanδ monitoring

High speed analog input channels

Synchronous acquisition

Digital signal processing

Bushing adapters for various tap design

Voltage RMS, Peak measurement

Overvoltage detection

Frequency and phase measurements

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System Architecture:

Končar bushing monitoring system is modular system and comes in two versions.

On-line bushing capacitance and tanδ

monitoring for 3 bushings (6 optional)


Advanced algorithms and analysis

tools

Built-in additional 8 analog inputs for

measuring load current, temperature,

humidity, etc.

Built-in additional 2 digital outputs

for alarm signaling

On-line bushing capacitance and tanδ

monitoring for 3 bushings (optional

up to 12 bushings)


Advanced algorithms and analysis

tools

Built-in additional 8 analog inputs for

measuring load current, temperature,

humidity, etc.

Built-in additional 2 digital outputs

for alarm signaling

Expandable system - analog input,

analog output, digital input, digital

output or RTD module can be added

to create complete transformer

monitoring system

Basic system – for 3 bushings

Expandable system – up to 6 additional modules






Measurements methods:

Končar Bushing monitoring can monitor bushings using 3 methods. Each method has its advantages

and disadvantages. Method selection has to be based on measurement requirements, available

conditions in substation and budget.

Advantages:

Simple method

Less cabling

High sensitivity

Disadvantages:

Network unbalance problems

Advantages:

No network unbalance problems

Monitors 6 bushings

Disadvantages:

More cabling

Available only if 2 transformers are

operating concurrently on same busbar

Advantages:

Absolute measurement

No network unbalance problems

Disadvantages:

More cabling

VTs are usually placed far away from

transformer and very often not available

Sum-of-phasors

Bushing to Bushing comparison

Voltage transformer reference






How it works:

Measuring path of the bushing monitoring system is shown on the figure

below. Signal is coupled from test tap of bushing by tap adapter and

measuring impedance. Measuring path provides safe connection to the

earth, thus preventing appearance of dangerous voltage at the test tap.

Several levels of voltage limiting devices are built-in test tap adapter,

measuring impedance and TMS cubicle.

Further, signal is connected to DSP (digital signal processor) which

measures amplitude and phase angles related to the signals from other

bushings or secondary terminal of voltage transformer.

In sum-of-phasors method, resultant phasor is calculated from signals of

3 bushings. Changes in capacitance and tan are then calculated from

resultant phasor. This technique provides very good sensitivity to

changes of tan because relatively small changes in resistive

component of leakage current cause big changes in resultant phasor.

Bushing-to-bushing comparison method is used for monitoring of 6

bushings for 2 transformers that are operating concurrently on same

busbar. While each set of bushing can be monitored independently

using sum-of-phasors method, this method gives more information by

comparing signals from pair of bushings that are operating on same line-

to-earth voltage. Changes in bushing capacitance and tan are

calculated from changes in phase angle and amplitudes ratio of leakage

currents.

If signal from secondary of voltage transformer is available, absolute

value of capacitance and tan can be measured by definition. This

method provides best results, but often it is not possible to use it

because there are no available VTs in substation or they are too far from

transformer.

TAP ADAPTERS






Additionally, Koncar Bushing Monitoring can detect peak value of fast

overvoltage (including 1.2/50 µs wave) that appears during switching of

transformer or atmospheric discharges. During overvoltage event, very fast

comparator detects that voltage is out of bounds and activates state-of-the-art

peak detector circuit which samples the peak value of overvoltage. Both,

positive and negative, peak values of overvoltage can be measured. Typical

signal waveform is given below:

This information is of great importance because insulation of

transformer and bushing can be damaged during those events.






Technical specifications:

Basic system – 3 bushings

General

Power consumption 25 W

Transient overvoltage protection up to 50 VDC

Power supply interruption protection 5 ms

Communication protocols:

IEC 60870-5-104, MODBUS/TCP

Power requirements

Power supply range 16.8 - 33.6 VDC


Physical characteristic

Dimensions (HxWxD) 150x277x171 mm

Weight 1.5 kg

Temperature range

Operating temperature range -40 to +85 °C

(IEC 60571:2006, Class Tx)

Storage temperature range -40 to +85 °C

Shock and vibration

IEC 61373:2010, Category 1, Class B

Electromagnetic compatibility

This product meets requirements of the

following standards:

EN50155:2007

EN50121-3-2:2006

EN61000-6-2:2007

EN61000-6-4:2005

Digital outputs

Number of channels 2

Relay type DPDT

Min. switching load 100 mA at 12 VDC

Maximum switching capacity

AC 1 A at 250 VAC

DC 1 A up to 50 VDC

DC 0.4 A at 120 VDC

Analog Input Module


AD resolution 12 bits

Frequency range 0-160 Hz

Update rate, all channels 1 ms

Input type – configurable current or voltage

Current 0 – 30 mA

Voltage ±30V

Bushing voltage transducer


Input voltage 0-300 Vpp

Monitored quantities

Relative Capacitance change resolution 0.1%

Dissipation Factor change resolution 0.05%






Technical specifications:

Expandable system

General


Transient overvoltage protection up to 50 VDC

Power supply interruption protection 5 ms

Communication protocols:

IEC 60870-5-104, MODBUS/TCP

Power requirements

Power supply range 16.8 - 33.6 VDC


Physical characteristic

Dimensions (HxWxD) 150x439x171 mm

Weight 3 kg

Temperature range

Operating temperature range -40 to +85 °C

(IEC 60571:2006, Class Tx)

Storage temperature range -40 to +85 °C

Shock and vibration

IEC 61373:2010, Category 1, Class B

Electromagnetic compatibility

This product meets requirements of the

following standards:

EN50155:2007

EN50121-3-2:2006

EN61000-6-2:2007

EN61000-6-4:2005

Digital outputs


Relay type DPDT

Min. switching load 100 mA at 12 VDC


AC 1 A at 250 VAC

DC 1 A up to 50 VDC

DC 0.4 A at 120 VDC

Analog Input Module



Frequency range 0-160 Hz

Update rate, all channels 1 ms

Input type – configurable current or voltage

Current 0 – 30 mA

Voltage ±30V

Digital Input Module


Input range 0-30 VDC

Input current 2.9 mA at 30 VDC

Transient overvoltage 2500 VRMS

Digital Output Module


Relay Type SPDT


AC 1 A at 250 VAC

DC 1 A up to 50 VDC

DC 0.4 A at 120 VDC

RTD module


Type 4 wire RTD


Update rate, all channels 0.56 s

Excitation current 2 mA

Data type Temperature (°C) or

Resistance (Ω)

Monitored quantities

Relative Capacitance change resolution 0.1%

Dissipation Factor change resolution 0.05%






Drawings:

Basic system – 3 bushings

Expandable system with up to 8 additional modules


Documents

Končar TMS - Bushing monitoring - Az-Teknik€¦ · Rajko Gardijan, dipl. ing. Samir Keitoue, dipl.ing. Head of Transformer Department Head of TMS section [email protected]