PLANNING, ELIGIBILITY FOR CONNECTION AND CONNECTION PROCEDURE IN EMBEDDED GENERATION

Transcription

1 PLANNING, ELIGIBILITY FOR CONNECTION AND CONNECTION PROCEDURE IN EMBEDDED GENERATION Presentation by Engr. O. C. Akamnnonu Chief Executive Officer, Ikeja Electricity Distribution Company

2 AGENDA WORK THROUGH INTRODUCTION SINGLE LINE DIAGRAM OF GRID NETWORK WITH EMBEDDED GENERATION BRIEF TECHNICAL DESCRIPTION ALTERNATIVE TYPES OF GENERATORS PLANNING AND CONNECTION OBJECTIVES PLANNING AND CONNECTION PROCESS PLANNING METHODOLOGY ADVANTAGES OF EMBEDDED GENERATION MAJOR CHALLENGES CONCLUSION

3 INTRODUCTION Embedded or Distributed Generation is usually a small scale production of power within the distribution network which does not have direct access to the transmission network. These generators are generally located close to the electricity consumer. They are typically owned and operated by retailers, single demand customers, local or state governments. The distributed generated systems are small in size, less than 10MW and typically 1.0 or 2.0 MW.

4 They feed into the distributed system directly, and may be installed by the utility or big customers. They may be of any type, but are most likely to be solar plants or wind energy plants. Figure 1 shows the single line diagram (SLD) of the electrical network as a whole showing the locations of both HV and LV distribution networks including HV and LV loads supplied by distribution networks and the possible locations of some embedded generators.

5 Transmission network (Hv) Sub-transmission network (HV) Terminal Substation Sub-transmission network (HV) (Hv) Distribution network (HV) Zone Substation HV LOADS LV LOADS Biomass Synchronous generator Combined Heat and Power (CHP) Synchronous generator Photovoltaic generator Connected via an inverter Figure 1: SLD of the grid network with embedded generators

6 BRIEF TECHNICAL DESCRIPTION: CLASSIFICATION EGs therefore may be classified into: Any generation interconnected directly with distribution facilities Commercial and stand -by diesel generators in hotels, hospitals and industrial plant sites. Residential generators typically 200W and up to 100kw Generation facilities installed near or at load centres Generators installed by a utility for voltage support or other ancillary services Any other generation between 100kW and 20-50MW, be it on or off-grid but connected at distribution level. Green power to reduce environmental issues.

7 ALTERNATIVE TYPES OF GENERATORS A variety of options exist in small and medium sizes EG application. Some of these are conventional thermal units (steam, gas), combustion turbines, fossil fuelled engines, micro turbines, fuel cells, internal combustion engine generators, micro, mini, small and medium sized. renewable technology options in PV Cells, wind turbines, bio-mass hydro schemes.

8 PLANNING & CONNECTION OBJECTIVES Embedded generation arises as a consequence of inadequacy of grid network coverage or poor voltage regulation of grid network. Existence of clusters of industries that require improved facilities for profitable operation. The distribution network should not be adversely affected by the interconnection of the EG in terms of the quality of supply, operational safety and efficiency.

9 The deficiencies arising from the interconnection of EG need to be cost- effectively minimized or optimized. There should be cost effective interface design and interconnection scheme.

10 PLANNING &CONNECTION PROCESS Stages Description 1. Project Planning Technical and commercial assessments, and initial contacts with Distributor on connection possibilities 2. Exchange of information Preliminary system studies on connection conducted to and preliminary plan determine connection cost 3. Project Design Power system studies carried out, and connection requirements detailed out, leading to the detailed design of the plant and its connection 4. Project Construction Construction of plant and the connection / reinforcement portion 5. Project Testing and Testing and commissioning of the plant and connection Commissioning reinforcement portion 6. Operation Co-ordination of the operation of the plant, with the distribution network

11 PLANNING METHODOLOGY S/ STAGE No 1. Preliminary System Study OBJECTIVES Preliminary system study carried out to ascertain the following: Capacity transfer limits, connection points and indicative cost, voltage and controls, fault level and losses. Basic connection requirements i.e. automatic disconnection, synchronization point, protection at network interface, basic monitoring requirement (status, voltage and power flows), metering point and system.

12 S/N o STAGE 2. Power System Study 3. Revisit studies conducted during preliminary studies OBJECTIVES To identify additional controls and protection and operating strategies for the EG plant when connected to the distribution network for the establishment of relevant specifications for the eg plan, and its interface with the distribution network. For more accurate evaluation of voltage profile and control based on accurate generator information. Specify control Determine fault level mitigation option

13 S/N TECHNICAL ISSUES ON CONNECTION AND GUIDELINES ISSUES RECOMMENDATION 1. Choices of voltage control for EG Power factor control Voltage control 2. Fault Mitigation Options EG contributes to higher system fault level Choices of fault level mitigation, responsibilities, and cost Critical limit fault level exceeds 90% of equipment rating EG to have both p.f and voltage control capabilities Preferred form of voltage control to be decided by utility based on simulation studies for each EG s case Study the options for each EG connection case. Generator impedance, reactor interfacing Transformers network splitting, current limiters. Etc. 3. Network and feeder capacity assessment To maximize EG output and transfer to local distribution system RE plants in low demand areas High cost of network reinforcement and connection Utility will propose point of connection for optimal power transfer and connection costs - while meeting all technical requirements.

14 S/N ISSUES 4. Reliability and power quality Minimal positive impact on EG on continuity of supply, due to islanding requirement Power quality: harmonics and flicker are non-issues as yet given existing type of EG generation 5. Protection and Controls Criticality of protection design and coordinated settings for safe operation of both EG and utility network Choice of loss of mains protection 6. System Losses System loss a limiting factor for RE capacity injection into remote distribution network Significant cost for losses and EG power transfer optimization Losses computation methodology under varying conditions NIL RECOMMENDATION Utility and EG developer to work closely at design stage of EG Seek right loss of mains solution based on each case Methodology and results on losses study to be transparent

15 CONNECTION PROCESS FLOWCHART FOR MICRO & SMALL EGs GENERATOR DISTRIBUTOR Submit Standard Connection Application Form to Distributor PRELIMINARY DISCUSSIONS Provide further information Is the information Sufficient Issue Connection Offer and Standard Connection Agreement SIGNED CONNECTION AGREEMENT

16 CONNECTION PROCESS FLOWCHART FOR MEDIUM EGs GENERATOR DISTRIBUTOR Initial connection enquiry to Distributor PRELIMINARY DISCUSSIONS Submit connection enquiry to Distributor Submit connection application to Distributor Check Application Is the information sufficient Is it more suitable to get an alternative Distributor Information to EG Info on agreement parties Review offer to connect Negotiate: Connection Agreement, Scope/cost of connection assets. Agree: Connection Agreement, Scope/cost of connection assets. Info on contestable works Preliminary programme Investigate application Amount Undertake of connection network application technical & fee economic studies Make Liaise generator with offer other to parties connect Access standards Connection terms and conditions Inform Generator Application of service competing standards application for network capacity Proposed scope of work SIGNED CONNECTION AGREEMENT

17 ADVANTAGES OF EMBEDDED GENERATION: for the Distribution Companies Transmission capacity relief Distribution capacity relief Hedge against high market prices Grid investment deferment Improved grid asset utilisation Improved grid reliability VAr support Voltage support Contingency reserves Energy and load management

18 ADVANTAGES OF EMBEDDED GENERATION: for Electricity Consumers Efficient use of energy from combined heat and electricity Improved reliability by having back up generation Incentives from utility to provide capacity reserve Low cost electricity Clean energy Improved power quality

19 ADVANTAGES OF EMBEDDED GENERATION: for the Commercial Power Producer Viable Power market to sell electricity Auxiliary services market (reactive power, stand-by capacity, etc)

20 MAJOR CHALLENGES SN CHALLENGE 1 COSTS Compensating EGs when selling their excess electricity to the utilities. Cost of distributing infrastructure for sparsely populated areas and with long distances between cities. Fuel cost can be an issue, especially in Nigeria where gas constraints exist near load centres. The availability factors for PV solar and wind turbines make them very unreliable and additional storage battery added seem to shoot the tariff beyond the capability of the consumers especially in rural areas. 2 SAFTEY if a line goes down, and whether the line is energized, the utility must know and respond safely.

21 MAJOR CHALLENGES cont 3 SYSTEM RELIABILITY CHALLENGE Off grid EGs must have some redundancy built into the scheme, so that the entire consumer cluster is not out for a single contingency fault. Voltage control and stability are other issues for an off grid EG and those other EGs connected to the grid will also experience many perturbations for grid instability. Without commensurate infrastructure upgrade to the network, a massive deployment of EGs can adversely affect regional distribution companies where many EG operators tied to the grid start switching their generators on and off. System stability becomes compromised with voltage flickers, power and frequency swing and sometimes voltage and system collapse may be experienced.

22 MAJOR CHALLENGES S N CHALLENGE 4 ENVIROMENTAL Siting and permit requirement 5 TARIFF Operators of EGs may not favour the approved tariff structure

23 CONCLUSION Advantages of EG tend towards evolution of a new modernized electric power system with greater flexibility and security. However, they need to be well coordinated so as not to pose an economic risk to existing utilities. Despite low level of EG penetration in Nigeria technical issues on connection of EG need to be adequately, consistently and transparently managed. There is need to educate all industry stakeholders no significant technical barrier to EG access. Guidelines would be put to test and accordingly reviewed by industry stakeholder as we come across better costeffective solutions based on our own or overall industry experience.

24 THANK YOU