IEC 61850 Protocol overview

What is IEC 61850 ??

• IEC 61850 is a global standard for “Communication Networks and Systems in Substations”

• It specifies an expandable data model and services

• It does not block future development of functions

• It specifies no protection or control functions

• It supports free allocation of functions to devices

• It is open for different system philosophies

• It provides the Substation Configuration description Language (SCL)

• It supports comprehensive consistent system definition and engineering

• It uses Ethernet and TCP/IP for communication

• Provides the broad range of features of mainstream communication

• It is open for future new communication concepts

History

• International Electrotechnical Commission (IEC) is global

• Publishes international standards for all electrical, electronic and related technologies.

• The IEC members are the national standardization organizations  i.e. not individuals nor companies.

• Experts in the technical committees represent their country i.e. not themselves or their employer

• IEEE and EPRI work under a similar charter in North America

IEC 61850:“COMMUNICATION NETWORKS AND SYSTEMS IN SUBSTATIONS”

• IEC 61850 is the first really global standard in the Electric Utility field

• Supported also in the ANSI/IEEE world

• Some 60 experts from Europe and North America have jointly developed the IEC v61850

• Includes the UCA 2.0 as a subset

• All 14 parts of the IEC 61850 were published in 2004/2005

• Influences other electric areas

• Wind power plants, Hydro power, Distributed Energy Resources.

• Implementation in progress by all major vendors

Objectives for the IEC 61850

Reduce cost from cradle to grave and into next generation:

• Interoperability

• IEDs from different vendors can exchange and use information over a common communications media.

• The functionality in different devices is however not necessarily the same. Therefore no interchangeability of devices from different vendors!

• Engineering and configuration data is portable between vendor tools

• Open IED description

• Reduces the engineering and configuration

• IEDs capabilities are described in a standardized way

• Proprietary functions, solutions, and data are still available and Allowed

• Communication closer to Power Apparatus

• Communication, data acquisition, and control capabilities will be directly imbedded into the primary equipment

• Free configuration

• Free allocation of functions in centralized or decentralized system configurations.

• Reduction of conventional wiring

• LAN instead of multiple copper wires

• Future proof

• Utility and Vendor investments shall be long lived in spite of fast changing technology

• The standard is able to follow the progress in communication technology as well as evolving system requirements.

Logical Nodes

• Functions or equipment used in power systems are represented in Logical Nodes, LN

• All information and functions in a substation is structured in atomic units, the LNs

• Each LN provides a list of well organized and named information Complex functions use a set of LN required to represent the function

• Services enable the exchange of the information in LNs between IEDs

• Example: the LN for a Circuit Breaker has the generic name XCBR

• New logical nodes can, if required, be created according rules defined in the standard

The substation LAN

• IEC 61850 specifies only the interface to the substation LAN

• The LAN itself is left to the system integrator

• The Ethernet LAN is a subpart of the station and needs engineering, configuration, supervision, and control as any other subpart

• A network management system is appropriate

• The LAN topology depends on a number of constraints:

• Operational requirements for the substation

• Size of the substation

• Reliability and availability

• The substation LAN as a whole will likely be separated into a station bus and one or more process buses

• Experience from previous substation communication architectures have shown that this is a sensible approach

Engineering and Configuration

• Savings from efficient IED engineering

• IEDs are engineered using manufacturer specific IED configuration tools

• Configuration tools translate the IED capabilities and configuration to the SCL (Substation Configuration description Language)

• SCL enables information exchange between IED configuration tools from different manufacturers

• SCL secures backwards compatibility between different versions of IEDs and IED configuration tools

Migration to IEC 61850

• Migration is technically possible as

• Replacement of station level devices

• Total or partial replacement of bay level devices

• Total or partial replacement of process level devices

• Extension with one or more bays

• Migration may not be profitable

• Two kinds of maintenance types in mixed installations

• No functional benefits

• Consider to migrate the total substation!

• Station computers and gateways will for long be compatible with current station bus protocols/interfaces

• Separation of communication and operator functions will allow for mix of station bus protocols, e.g. IEC 61850-8-1 and LON

• Problems if the station bus is used for station wide fast functions, e.g. interlocking, transfer between two buses may take time

Migration on Bay and Process levels

• Replacement of single IED

• Replace with plug compatible IED, if possible an IEC 61850 compatible one

• Retrofit of bay

• Select an IEC 61850 compliant set of IEDs, vendors will have IEC 61850 compliant IEDs with interfaces compliant to today's

• Extension with new bay

• As for retrofit but consider also a full process bus

• Retrofit of primary equipment or transducer/actuator

• Same as retrofit or new bays

Conformance Tests

• The conformance tests include verification of the vendor provided information and tools, as for example

• The formal SCL description of the IED in the ICD file, IED Configuration Description file

• The SCD, System Configuration Description, file that describes the system used for the verification of the IED.

• Conformance tests can be performed by the vendor himself or by an independent test organization as KEMA

• Interoperability between products from different vendors guaranteed by

• Quality Assurance program during development, market introduction, and project execution

• Conformance tests as type test for the communication capabilities

IEC 61850 – Benefits and Conclusions

• The standard for substation automation!

• Higher degree of flexibility though interoperability between IEDs from different vendors

• Taking full advantage of future innovations within Substation Automation and communication technologies

• Promises cost reductions from design to operation and maintenance!

• Substation architecture adapted to your requirements

• Gives the opportunity to select ‘Best value for money’

• Embraced by vendors and users equally!

Basics of Conditional monitoring of power transformer

Types of monitoring

• Behavior monitoring
• Periodic monitoring
• Online monitoring
• Diagnostic monitoring

Behavior monitoring

• Operating temperatures
• Noise level
• Oil levels
• Flow indicators

Periodic monitoring

• Impedance measurement
• Capacitance& tan delta of windings /bushings
• No load losses
• Magnetic balance
• Mag current
• Oil tests
• Dissolved gas analysis

Oil tests

• Breakdown voltage
• Moisture content
• Acidity
• Tan delta
• resistivity

Dissolved gas analysis

• Type of fault gasses
• H2  partial discharges
• Co   cellulose involvement
• C2 h2     acetylene  arcing
• Ch4 , c2h4, c2h6,  thermal hot spots
• Frequency of DGA
• Decision on investigation

Online monitoring

• Online dga
• Online PD

Diagnostic monitoring

• Low voltage tests
• Loss measurement
• Voltage ratio
• Resistance
• Frequency response analysis
• Degree of polymerization index
• Furan analysis (furfural content)

Frequency response analysis

• To detect movement of windings under short circuit conditions
• Low voltage sinusoidal output to one end of winding from network analyser
• Voltage transfer function measured from 5hz to 10mhz
• NA programmed to measure amplitude  and phase shift at discreet intervals of frequencies
• Condition assessment based on

      1. Comparison  of responses from different phases for each winding and tap position

       2. Comparison of responses from different transformer of the same design response comparison

• Response for all three phases to be similar on a particular tap position for a single transformer and for different transformer of same design
• Appearance of new features or major phse shift is concern.
• Transformer windings LC  network responses governed by inductance/capacitance of network

Frequency bandwidths

• 5hz  to 2khz indicate mag circuit condition
• 2khz  to 200 khz   changes in leakage impedance
• 1mhz and above  indicate capacitance changes

DP INDEX

•  Kraft paper used as insulation is a mat of cellulose fibers which consist of cellulose molecules
• Cellulose a linear polymer of glucose molecules that are linked by glycosidic bonds.
• Length cellulose molecule is measured in terms of DP Index.

Mechanical strength  of paper

• Depends on dpindex of paper
• New paper   1200 to 2000
• Below 250  a matter of concern
• Below 150 little life left and close to failure

Furfural analysis

• Product of cellulose  degradation are furan compounds particularly 2-furfural dehyde
• Compounds stable up to 110 degree centigrade
• Presence of compounds in oil is certain indication of cellulose degradation

Power Line Carrier Communication (PLCC)

PLCC system uses the same High Voltage transmission line connecting two sub-stations for telecommunication purpose too.

PLCC is used in all power utilities as a primary communication service to transmit speech, telemetry and protection tripping commands. This is economic and reliable for message transfer as well as low bit rate RTU signals.

PLCC

1.    The voice/data are mixed with radio frequency carrier (40-500kHz), amplified to a level of 10-80W RF power and injected in to high voltage power line using a suitable coupling capacitor.

2.    The power line as a rigid long conductor parallel to ground, guides the carrier waves to travel along the transmission line.

3.    Point to point communication takes place between two SSB transceivers at both ends.

4.    The signal that can be transmitted over the PLCC include

• Speech signals

• Data/Telemetry signals

• Signals required for Tele protection.          

Importance of PLCC

1.    PLCC is used for conveying these information without any interference with normal power flow.

2.    The concept of GRID has been developed for the effective utilization of available electrical energy.

3.    Load Despatch centre will be required to monitor & control the electrical network.

4.    The LD centre have to process & act upon data (MW,MVAR, KV etc).

History

The first PLCC system was introduced by an American company in 1920.

The power line conductors were used for communication instead of separate

telephone lines.

In India PLCC system was introduced for speech & protection in 1950.

Line trap or Wave Trap(WT)

·         Name itself suggests that it traps the waves /frequencies of High magnitude.(50 KHz to 500 KHz)

·         WTs are provided to block the carrier signals from entering in the sub-station and to allow the power frequency current to pass through.

·         Achieved by providing a suitable filter consisting capacitors & inductors.

·         L. A. is provided across WT to protect it from high voltages surges.

Working Principle

• PLCC works on Modulation & Demodulation.
• Modulation & Demodulation requires carrier frequency which is generated in in cabinet.
• Crystal Oscillator generates carrier frequency.
• PLCC panel/terminal/cabinet/set consists of Audio Frequency (AF )section

Transmit path

1. The speech signal along with other Voice
2. Frequency signals is fed to IF modulator.

• IF modulator modulates the AF signals to IF stage.

• Up converter converts IF to HF.

• HF signal is fed to preamplifier & then to Power amplifier t raise the output level t required value.

• The amplified signals are then fed to HF hybrid.

• Hybrid is used to provide isolation between Tx & Rx path at HF stage.

• HF signals are then connected to HF Cable.

Receive Path

·         The receive section receive the signals from remote end through HF Hybrid.

·         Down-Converter converts the signals from HF to IF in connection with a band pass filter which allow only the required signals having a certain band.

·         Demodulator demodulate the signals from IF to AF.

·         Speech, data & other superimposed channels are separated out with suitable filters,

Importance of Pilot

A pilot frequency is provided for self-monitoring & Automatic Gain control (receiver volume control).

• Pilot indicates the healthiness of cabinets.

• Pilot freq.is transmitted during normal rest condition & shifted dial is transmitted during dialing for transmission of pulses.

• A dc signal whose amplitude is proportional to receive signal is fed to the amplifier in Rx section to control the gain of the amplifier.

Frequency allocation in PLCC

·         HF band 50 KHz to 500 KHz

·          Voice Frequency 0.8 to 1 KHz.

·          Data channel freq. called as AF 1 to 4 KHz.

·         Pilot freq. 2.5 to 4 KHz.

·          IF 24 to 28 KHz.

·          Bandwidth 4 or 8 KHz

Coupling Capacitor

Offers isolation between the high voltage line and carrier equipment.

•  It offers minimum impedance to carrier frequencies (50 KHz to 500 KHz)and high impedance to power frequency( 50 Hz).

•  The top end of C.C. is connected to the high voltage line and lower end is connected to the earth through LMU.

Specifications of WT & CC

Wave Trap

• 2000A/ 1.0 mH

• 1250 A/ 0.5 mH

• 630 A / 0.5 mH

• Tuning pot

• Freq. Band

• Blocking impedance

• Blocking Resistance

Coupling Capacitor

• Rated capacitance:-

– 400 kV-4400pf

– 220 kV-6600pf

• Attenuation in dB:-0.5 dB

• Pass Band- 50 to 500 kHz

Connection of WT & CC

Line Matching Unit

Name itself gives idea that this unit matches something. This something is nothing but Line impedance.

• It is mounted at the base of the coupling Capacitor.

• LMU consist of 2 units called unit A & unit B

• Unit A consist of

– Balancing T/F

– Matching T/F

– Filter unit.

• Unit B consist of

– Matching T/F

– Filter unit.

Balancing Transformer

– It improvises better Ph. Splitting & couples the o/p of PLCT to the coupling filters.

– It ensures the carrier signals are in healthy condition even under the failure of any of the coupled phases & voltage isolation.

• Matching Transformer

– Impedance matching & high voltage isolation.

• Capacitor Filter together with CC forms

Three element protective device

Lightening Arrestor

– Protects coupling device from high voltage spikes from power line that appear at the bottom of coupling condenser.

• Drainage Coil Offers low impedance to power frequency and high impedance to carrier frequencies, thereby power frequency current flowing through coupling condenser gets grounded and protects the coupling device.

• Earth switch

– Normally this is kept open but is closed

Technical specifications

LMU

– Operating Band width- 80-500 KHz for CC 4400 pf.

– Composite loss- < 2db.

– Return loss > 12 db

– Equipment side Impedance- 75 Ohm

– Line side Impedance- 600 Ohm ph. to Ph.

– Peak envelope power- 650 W

LA

– Rated Volt.- 850 V

– P.F. spark Over Volt.- Twice rated Volt.

Drainage Coil

• Rated Inductance- 40 mH
• Cont. Current rating- 1 Amp.
• Short time current rating- 50 Amps.

Earth Switch

– insulation withstand Volt.- 10 KV AC

– Rated current- 400 Amps

Types of Busbar Scheme & Substation

Types of Busbar scheme

 Single busbar

 Double busbar with one breaker per circuit.

 Double busbar with two breakers per circuit.

 Main and transfer bus

 Ring bus

 Breaker and a half arrangement

 Mesh arrangement etc.

Structural arrangement

1.    Design of towers and beams

2.    Fabrication drawings of tower & beams

3.    Tower foundation and their designs

4.    Design of equipment supporting structure

a)    CT

b)    CVT

c)    LA

d)    Bus Post Insulator

e)    Isolator

f)     Wave Trap

g)    Circuit Breaker

5.    Equipment supporting structure fabrication drawings

a)    CT

b)    CVT

c)    LA

d)    Bus Post Insulator

e)    Isolator

f)     Wave Trap

g)    Circuit Breaker

6.    Details of foundation bolts

a)    Equipment Structure

b)    Gantry Structure

7.    Design of equipment foundations & foundation details

8.    Cable trench layout

9.    Cable trench section details

10. Cable trench road crossings

11. Marshalling box foundation

12.   Sump pit

Types of substation: 

The substations can be classified in several ways including the following:

i)             Classification based on voltage levels e.g.:

ii)            AC Substation: EHV, HV, MV, LV; HVDC substation

iii)           Classification-outdoor or indoor.

iv)           Outdoor substation is under open sky. Indoor substation is

v)            inside a building.

vi)           Classification based on configuration, e.g.:

a.    Conventional air insulated outdoor substation or

b.    SF6 Gas Insulated Substation (GIS)

c.    Composite substations having combination of the above two.

vii)         Classification based on application.

a.    Distribution substation

b.    Switchyard in Generating Station

c.    Switching substation (without power transformers)

d.    Sending-end substation

e.    Receiving substation

f.     Factory substation

g.    Compensating substation e.g. having static var compensation etc.

Features of a AC Substation & HVDC subsation

An AC Substation has following parts:

 AC Switchyard

 Control Building

 DC Battery System and LT Distribution System

 Mechanical, Electrical and other auxiliaries

 Civil works.

An HVDC substation has following main parts:

 AC Switchyard

 Converter Transformers

 AC Filter banks

 Valve Halls

 AC Switchyard, Smoothing Reactor, DC Filters

 Mechanical, Electrical and other auxiliary systems