The electrical distribution system in Trinidad and Tobago presently contains equipment which meets the basic demands with regard to its protective map. . Presently a manual method is used to turn up and extenuate against the loss of electrical supply.
Any betterments in the location and handling of mistake conditions on the distribution web will enable for a more efficient and effectual service to clients. The electric resistance based mistake location method was selected after a reappraisal of the methods presently available for mistake location. The suitableness of autoreclosers, sectionalizers, and motorized switches was examined in assorted system constellations to enable effectual direction of the web for supply Restoration.
It is proposed that the mistake location method be combined with the optimized constellation of equipment in the distribution web utilizing a Programmable Logic Controller ( PLC ) system to enable an machine-controlled response for supply Restoration.
List of Illustrations
Figure 1: System Diagram of the Outer West Ring ( sourced from T & A ; TEC Transmission System Diagram 2009 ) 4
Figure 2: Transmission Lines Associating the Substations of the Outer West Ring ( courtesy T & A ; TEC Transmission Department ) 5
Figure 3: Single Line Diagram of Diamond Vale Substation Feeders 6
Figure 4: Single Line Diagram of Diego Martin Substation Feeders 6
Figure 5: Full Feeder Schematic for Diamond Vale Substation 7
Figure 6: Full Feeder Layout for Diego Martin Distribution Substation Feeders 8
Figure 7: Westmooring Substation Single Line Schematic 8
Figure 8: The Main Feeder chosen for Analysis ( shown in blue ) 10
Figure 9 A Typical Distribution Feeder with Two Beginnings 18
Table 1- Actions Required due to System Occurrences 19
List of Abbreviations
Trinidad and Tobago Electricity Commission ( T & A ; TEC )
Regulated Industries Commission ( RIC )
Outer West Ring ( OWR )
Air Break Switch ( ABS )
University of Trinidad and Tobago ( UTT )
The Trinidad and Tobago Electricity Commission ( T & A ; TEC ) presently has stated accomplishable ends based on the Regulated Industries Commission ( RIC ) demands for the supply of electricity to clients.
The distribution system presently experiences jobs related to unplanned outages. These jobs are solved by the appropriate forces on responsibility ( Senior Foremen, Engineers or Emergency Crew ) utilizing trouble-shooting techniques. Troubleshooting of the system would by and large be done by following of the peculiar system ( feeder ) based on the studies of the outage ( s ) as received from the country Telecommunication Operator ( s ) .
Factors which affect the response clip include:
Extent of the outage ( figure of clients without supply )
Number of outages in a given clip period ( limited resources to react )
Location of the system perturbation ( Distance to go and/or topography of the country )
Skill and experience of the Duty forces in troubleshooting of the job
Timely response of the Duty and/or exigency forces
Switch overing required for returning supply to the affected clients ( permissions required, figure of equipment to be activated )
Optimization of the distribution web via automated mistake location and response will help in accomplishing effectual and efficient system operation.
On completion of the undertaking the following would hold been attained:
Design of a mistake location system which would find the specific sidelong feeder on which a three stage to earth mistake occurs
Design of a Supply Restoration Program to insulate the faulted system via an automated response
in an optimized theoretical account of a selected Primary Distribution Feeder in the Outer West Ring ( OWR ) of T & A ; TEC ‘s distribution system.
To be done:
Analysis of the bing Outer West Distribution Network.
Choice of a specific Primary Distribution Feeder system to implement the mistake location and response scenarios.
Response of the location and exchanging systems to a three stage to earth mistake
Choice and usage of current available engineering for mistake location in Distribution Systems.
Design of a Programmable Logic Control system to help the machine-controlled mistake response map.
Principles of operation of the protection schemes normally used on the current T & A ; TEC Distribution Systems.
System Occurrence of other mistake types ( limited to the type of mistake stated )
Economic feasibleness of implementing the machine-controlled systems developed.
Blackout response scenarios.
A mistake location system using the electric resistance line mistake turn uping theoretical account.
A system response plan which responds to imitate mistake ( s ) by isolation and returning supply to the largest figure of clients.
Description of the Outer West Ringing
Figure 1: System Diagram of the Outer West Ring ( sourced from T & A ; TEC Transmission System Diagram 2009 )
Located in the western side of Trinidad, the OWR of the T & A ; TEC Transmission web ( see Figure 1 ) consists of the undermentioned substations: Chaguaramas ; Carenage ; Pt. Cumana ; Mt. Pleasant ; Diamond Vale ; Diego Martin ; and Westmoorings.
The substations of the signifier a ring web which is supplied chiefly from two 66kV ( 500Ampere ) transmittal lines, every bit good as one 33kV ( 310 Ampere ) line supplied via an Air-Break Switch. The 66kV transmittal lines are connected to the 66kV coach at the Wrightson Road substation while the 33kV line is located at Action Court. A link at the Westmooring Substation connected to an Air-Break can be used to short-circuit the two 50/70 MVA Power Transformers if the demand arises. Use on the Outer West Ring is about 42 MW during the twenty-four hours and 52 MW at dark ( T & A ; TEC Control Figures ) .
The country contains a mix of commercial and residential users of electricity. The Chaguramas country is home to marine activity ( ship fixs, angling industry, yachting ) , whilst the Diamond Vale, Diego Martin, Carenage countries are chiefly residential lodging ( see Figure 2 ) .
Figure 2: Transmission Lines Associating the Substations of the Outer West Ring ( courtesy T & A ; TEC Transmission Department )
Choice of a Typical Feeder for Analysis
In reexamining the OWR the Diamond Vale ( Figure 3 ) and Diego Martin ( Figure 4 ) substations feeders were shortlisted ( note- Figures 5 and 6 show the geographic layout of these feeders ) . These two were shortlisted because of the simpleness in the distribution design and the particular clients being chiefly residential ( Westmooring Feeder ( Figure 7 ) for illustration was non selected because of the commercial facet ) .
Figure 3: Single Line Diagram of Diamond Vale Substation Feeders
Figure 4: Single Line Diagram of Diego Martin Substation Feeders
Figure 5: Full Feeder Schematic for Diamond Vale Substation
Figure 6: Full Feeder Layout for Diego Martin Distribution Substation Feeders
Figure 7: Westmooring Substation Single Line Schematic
Analysis of the Selected Distribution Substations
( Diamond Vale and Diego Martin )
Diego Martin was selected for the undermentioned grounds:
System Topography – Simplicity of the feeder circuits
Accessibility to system – merely off the Highway on chief roads in Diego Martin
Lower Happening of offense in this country
“ Resident of Diamond Vale, Diego Martin, and the environing countries are naming on the relevant governments to dispatch frequent constabulary patrols as they claim that there have been a batch of robberies and auto jackings. ” ( Trinidad and Tobago Newsday, 2007 ) . Diamond Vale has been a offense “ hot topographic point ” with a assortment of shots attributed to packs.
Analysis of the Specific Feeder
The feeder circuit shown below was selected because of its simpleness of design. The feeder circuit exits the Diego Martin S/S traveling south along St. Lucien Road. An unfastened subdivision feeder goes toward the Majuba Cross Road Feeder system ( the diagram indicates a separation which can be linked if required ) . The chief feeder ( St. Lucien Road ) goes south bound towards Sierra Leone Avenue. At Sierra Leone the feeder tees off traveling west towards the usually unfastened Air Break Switch # 21 ( ABS ) and east towards another usually unfastened ABS # 34 ( see Figure 8 below ) .
Figure 8: The Main Feeder chosen for Analysis ( shown in blue )
Presentation of Findingss
Methodology for Gathering Data
Subsequent to treatments with my supervisor with whom my initial thought for the undertaking was discussed the specific thoughts were all right tuned. Discussions were held with the Planning Department of Distribution North ( T & A ; TEC ) with respects to the individual line diagrams of the OWR every bit good as the needed inside informations of the feeder circuits ( common mistakes ( see Appendix A ) , system burdens, electromotive forces, line distances, and electric resistances ) .
Requests were made to the Protection and SCADA Department for information on specific jobs encountered in developing the pilot undertaking presently being done in the Eastern Distribution Area. Since the undertaking is presently under development really limited feedback was given. Interviews were done with forces of Planning Department ( every bit good as with applied scientists in Protection Department ) with respect to the feasibleness of implementing the mistake location in the distribution system. ( see the sample inquirer in Appendix B )
Research on the cyberspace was besides done with visits to assorted maker web sites for information and equipment specifications ( ABB, NOJA Power ) .
Membership in the Institute of Electrical and Electronic Engineers ( IEEE ) ( Member # 91110850 ) besides allowed entree to a library of proficient articles and research documents.
The library at the University of Trinidad and Tobago ( UTT ) besides provided suited mention stuff for comparing of the assorted methods employed in mistake location and system mechanization.
Mistakes common ( in order of regularity of happening ) in the OWR ( Appendix A ) include:
Defective Equipment ; Loose Connections ; Tree Contact ; Lightning ; Vehicles ; Cable Faults ; Kites.
Mistakes largely occur as mechanical dislocations and supply Restoration can be quicker if the mistake location can be rapidly determined. Locating mistakes on distribution systems is different from that of transmittal systems ( mistake location in transmittal systems is a good developed technique ) since factors such as topology and operating restraints ( e.g. non-homogeneous feeders, burden lights-outs, laterals, radial operation, the handiness of mensurating equipment ( Short, 2003 ; Mora-Flurez et al. , 2009 ) restrict the engineering being transferred. Distance location ( s ) obtained can mention to multiple locations since distribution feeders can dwell of multiple sidelong lines ( the mistake location can be along any of the laterals ) . Imbalances due to the untransposed lines along with the presence of individual and three stage loads farther perplex the procedure. Common electrical mistakes in distribution systems are short circuits including: individual line-to-ground, line-to line, dual line-to land, three-phase and three phase-to-ground mistakes ( each can happen with differing values of mistake opposition ) .
Options and Selection Criteria for Methodologies
Common Methods of Fault Location
Methods applied to a distribution system for mistake location are categorised into three wide classs:
Electric resistance and related Fundamental Frequency Component Based Methods,
High frequence constituents and going moving ridge based methods
Knowledge-based Methods ( can be divided into three farther groups: Artificial intelligence and Statistical Analysis ; Distributed Device ; and Hybrid )
Electric resistance Method
In this method the distance of the mistake from the primary distribution coach to the mistake location is estimated by utilizing the electromotive force and current values measured at one terminal ( or two terminals of the line ) . Mathematical equations are so used to gauge the mistake location.
The mistake types and faulted stages are foremost identified so the evident electric resistance is calculated based on the selected electromotive force and selected current. Load currents at different lights-outs are by and large non considered and will be beginnings of mistake ( Girgis, 1993 ) .
The chief drawback of impedance-based methods is the multi-estimation due to the being of multiple possible faulty points at the same distance. Consequently, these methods provide precise but unsure mistake locations.
High Frequency Components and Travelling Wave Based Methods
The position of this method was based on the contemplation and transmittal of the mistake generated going moving ridges on the faulted power web ( Thomas et al. , 2003 ) . With this technique a mistake can be located with high truth.
Disadvantages include the fact that the execution is complex ( excess equipment, such as the GPS system, mistake transient sensors and diagnostic package ) and more expensive than the execution of electric resistance based techniques.
Artificial Intelligence ( AI ) and Statistical Analysis Based Methods
These methods include: Artificial Neural web ( ANN ) , Fuzzy Logic ( FL ) , Expert System ( ES ) and Genetic Algorithm ( GA ) . These methods can assist operators or applied scientists in that a batch of computations can be done in a short period of clip. The clip for turn uping a mistake ( s ) is well reduced and human errors are avoided.
The chief disadvantage of this method is that heavy calculating power is needed to run the plans.
Distributed Device Based Methods
A mathematical attack is used which located mistakes based on installed electromotive force detectors, an information database and the web ‘s topological construction ( Wang et al. , 2000 ) . The relation of the electromotive force detectors with subdivisions was formulated as a matrix. Another matrix was constructed based on the topological relation between subdivisions and nodes in an electric web. Matrix operations were so used to find all faulted subdivisions. The disadvantage of this technique is that mistakes may ne’er happen in the parts calculated while the electric resistance of the mistake can change even in deliberate locations.
While some methods locate mistakes based on one algorithm, the intercrossed methods that locate mistakes based on more than one algorithm therefore giving a more accurate mistake distance. Subsequent to the happening of the mistake values of current or electromotive force was used to cut down the multiple appraisal consequences ( Zhu et al. , 1997 ) . This method besides required circuit simulation to enable the operation of a peculiar combination of protective devices and to let the burden alteration form during different mistake scenarios to be recorded.
Disadvantages include: the diagnosing and modeling of the circuit and simulated mistake scenarios were time-consuming. The modeling procedure is besides required for each peculiar system.
Choice of the Fault Location Method
By comparing the advantages and disadvantages of the assorted methods the Impedance Method is proposed for usage in this paper at this clip ( within the clip restraints for the Phase One presentation ) .
It is proposed that appropriate choice and arrangement of equipment ( see Section 8- Equipment Selection ) in strategic locations be used to augment the applied algorithm which along with a PLC constituent will enable for cut downing the mistake associated with the feeder laterals.
The choice and arrangement of the appropriate equipment type and functional features will organize the anchor for an efficient and effectual mistake location and system response plan. The chief equipment required to supplement those bing will be described below.
An auto-recloser is a pole-top mounted circuit ledgeman which has the ability to automatically reclose. The usage of the auto-recloser has allowed for a broad assortment of operations in distribution systems. This particular type of circuit ledgeman is used to protect subdivisions of the overhead distribution line system by utilizing an electronic control unit to enable the gap of the chief contacts of the ledgeman when it detects fault currents on the overhead lines. The control unit will enable a recloser map which will enable the chief contacts to shut after a preset clip. If the mistake is still present the chief contacts will open and shut once more ( can be programmed for up to two more times ) before eventually locking out ( remaining open ) . If the mistake has cleared during the unfastened portion of its operation the sequence of operation terminals with the chief contacts staying closed ( clients are hence still supplied ) .
Other utile characteristics include: Load Monitoring ; Fault Monitoring ; Directionality of Protection ( ability to trip in each way ) ; Under / Over Voltage and Frequency ( can supervise, dismay and command these events ) ; Power Quality Monitoring ; and Flexibility of Use ( can be programmed for assorted systems ) ( ABB, 1999 ) .
These switches look really much similar to the auto-recloser. Different functionalities differentiate between the two as follows- the sectionaliser does non disrupt mistakes but alternatively counts the figure of happenings of mistakes so opens during the de-energised clip in the line. The interrupting device is normally the auto-recloser or a circuit ledgeman in a substation.
This particular switch is a feeder selective device which requires a chief line device to run before its ain operation.
This type of switch costs less than the auto-recloser and can be used for- distinct timing ; cold burden override ; one-shot operation.
These switches are typically manually operated air interruption types designed for local operation. Basic constituents in any system motor operated types are besides available.
Distant operation will let for the reconfiguration of a circuit such that supply can be restored to as many clients as possible.
Switchs are simple devices which do non run under burden and let for a seeable interruption in the system to ease fix work.
Configuration of the Feeder Equipment
The diagram below ( Figure 9 ) shows a individual line layout of a feeder with Substation Circuit Breaker ( SS CB ) , two usually closed autoreclosers ( R1 and R2 ) , and a usually unfastened switch ( R3 ) . ( Basic construction similar to the Diego Martin feeder being considered. )
Figure 9 A Typical Distribution Feeder with Two Beginnings
( Diagram courtesy NOJA Power Co. Ltd. )
The aims of such a constellation is to observe a loss of supply from the original beginning due to a coevals failure or a mistake in the system exchanging to automatically reconstruct supply to the unaffected country.
To enable an appropriate response the undermentioned regulations will use:
R1 – opens to forestall back feeding to the substation
R2 – requires directional protection to supply equal protection during reversal of the supply way.
R3 – shall shut on loss of supply from SS 1
Situations which were considered and the needed actions are shown in Table 1.
Action ( s ) Required
Loss of supply from Substation # 1
Substation 1 demands to be isolated and the web needs to be reconfigured to supply an alternate supply from Substation 2.
Mistake Between R1 and R2.
Faulted line subdivision must be isolated and supply restored to the un-affected country ( s )
Mistake Between R2 and R3
Faulted line subdivision of the Line must be isolated and supply restored to the un-affected country
Table 1- Actions Required due to System Occurrences
Each of the “ Action ( s ) ” required ( Table 1 ) will necessitate specific consecutive stairss of operation in order to accomplish the require operation ( s ) as follows- :
Break of supply from SS 1:
R1 recloser detects Loss of Supply ( UV3 ) and opens after a preset clip T1.
R3 recloser detects Loss of Voltage on one side and stopping points after predetermined clip T2.
Time T2 & gt ; Loss of Supply clip T1.
Recloser R2 provides line protection in either way.
Mistake between R1 and R2:
R1 recloser performs preset figure of protection trips and goes to Lockout ( T1 – entire clip of recloser sequence )
R3 Recloser detects a Loss of Voltage on one side and Stopping points after clip T2
After Closing of R3 recloser onto the mistake, R2 recloser goes to lockout province after a pre-set figure of protection trips.
Other unaffected countries are returned to provide.
Mistake between R2 and R3:
R1 – detects the mistake but R2 recloser performs the protection operations and goes to Lockout.
After clip ( T2 ) expires, the R3 Recloser closes onto the mistake and so trips to lockout.
Choice and arrangement of the extra equipment ( auto-reclosers, sectionalisers and switches ) into the selected feeder for implementing the Fault Location and Supply Restoration program.
Choice of the computations to work out the specific electric resistance algorithm ( suited for the chosen feeder system of the Diego Martin Feeder ) .
Modeling and Testing of the Fault Location and Supply Restoration Plan.
The primary distribution systems in Trinidad and Tobago have been placed really low in importance on the list of precedences of the company responsible for administering the electrical supply. Protection and mistake location systems have been good developed for the transmittal web in the state. Recently there has been a displacement in the paradigm of T & A ; TEC and focal point has been shifted to the distribution web. A pilot undertaking in the Eastern distribution Area ( Watts Happening Magazine, September to December 2010 ) is being used to find the feasibleness of implementing such a system.