Power Quality: Fouad Dagher
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Power Quality: Fouad Dagher NY's Regional Energy Efficiency Conference Parts of the Electric System 1. Generating Station: Produces Electricity. 2. Transmission Lines: Move electricity great distances at high voltage. Typically 115,000+ volts. 3. Transmission Substation: Redirects power delivery and provides switching/fault protection. 4. Distribution Substation: Lowers the voltage for delivery on local streets and provides switching/fault protection. 5. Distribution Lines: Delivers electricity to neighborhoods. Typically lower than 15,000 volts. 6. Service Wires: Connects individual buildings to the grid. Typically lower than 480 volts. 2 Power System Components Generation – Large central high voltage plants & small DG Transmission – 765 to 115 KV Sub-Transmission – 69 to 23 KV Primary Distribution – 13.2 to 4.16 KV Secondary Distribution – 480, 208, 120 volts 3 Dunkirk Coal Plant - 600 MW Wind Turbines on Lake Erie 20 MW 4 Lewiston Pumped Storage Plan 2,300 MW Manchester St Gas fired plant 450 MW 5 WNY Transmission System 345 kV Cross State System G NYPA G G Dunkirk 230 kV New York G NYPA G G Dunkirk 115 kV System (WNY) 23 kV System 13.2 kV Dist 4.8 kV Dist 4.16 kV Dist 6 Sec Customers 120/240 V, 208Y/120 V, 480Y/277 V 34.5 kV Subtran HV Customers 230/115/34.5/ 13.2/4.8/4.16 KV Sec Customers 120/240 V, 208Y/120 V, 480Y/277 V Distribution Equipment (Cont.) Disconnect Switch Open or close to temporarily reconfigure a feeder. 7 Distribution Equipment (Cont) Capacitor Bank Improves power factor on the feeder Helps to raise feeder voltage during peak loading condition Can cause a voltage surge or transient when turned on This version operates automatically , most are fixed banks that are ‘always on’. 8 Distribution System Equipment Pole top recloser Opens to clear faults Automatic reclosing to restore the circuit after a temporary fault. Collects fault information Monitors voltage and current 9 Distribution Equipment (Cont.) 3 Phase Riser pole Overhead to underground transition Fused cutouts can open to protect equipment from fault current Lightning arrestors protect equipment from high magnitude transients 10 Distribution Equipment (Cont) Three Phase Pad Mounted Transformer Typical device used to provide service to a business or building Steps voltage from distribution voltage to service voltage Generally the line of demarcation between utility and customer is the secondary terminal, also known as the service point. 11 Distribution Equipment (Cont.) Overhead 3 phase Transformer Bank Provides 3 phase service voltage to customers served from an overhead system Fused cutouts and lightning arrestors protect equipment from fault and surge conditions For overhead service to a building the service point is the connection between the triplex and the service conductors at the building. For underground service laterals, the service point is at the transformer. 12 We have a large system to maintain Asset Elements Distribution Poles 1,212,965 Transmission Poles 600,000 Transmission towers 22,000 Overhead Transformers 13 Pad Mount Transformer 57,000 Switchgears 2,700 23 kV – 345 kV - Circuit Miles 9,300 mi. Primary Voltage - Circuit Miles 42,000 miles Secondary Voltage - Circuit Miles 18,250 miles Substations 894 Problems Animal Contacts 15 Tree Contact 16 Motor Vehicle Accidents 17 Storms 18 Equipment Failure 19 “Direct” Distribution System Disturbances Fault occurs on the feeder Substation A directly serving the customer. Circuit Breaker If the fault occurs on the main ‘back-bone’, customers on the customer load Fuses feeder will experience up to Circuit Reclosers three re-close attempts and maybe a total loss of power for customer load an extended period of time. If the fault occurs on a ‘sidebranch’, a fuse may isolate the fault. Customers on the branch circuit will lose power and other customer’s on the feeder will 20 experience a brief ‘blink’ or ‘dip’ Switches customer load “Indirect” Distribution System Disturbances Substation A Substation B fault occurs on an Circuit Breaker ‘adjacent’ feeder within the same substation as the line customer load Fuses Circuit Reclosers Customer’s on adjacent customer load Switches serving the customer. customer load normally open tie switch feeders may experience several brief ‘blinks’ or ‘dips’ as the substation attempts to restore power – recloser normally open tie switch 21 attempts. What is National Grid Doing to improve reliability? Program Feeder Hardening Targets Lightning, Tree, Deteriorated Equipment, Animal Protection 22 U/G Distribution Programs Cable and OFC Replacement O/H Fused Cutout Replacement Replace Faulty Cutouts Vegetation Management Growth Management Cycle Augmented Clearance for Trees Problem Trees Inspection Programs Substation, OH & U/G Systems Specific Area Activities Special Projects Why does my equipment trip during faults on utility system? Not enough voltage – if there is not enough voltage to provide the energy, equipment will trip. Undervoltage circuitry – meant to monitor the voltage and trips the circuit if voltage goes below a predefined level. Unbalance protection- faults don’t affect all phases equally voltage imbalance will result. Emergency off circuitry that monitors several parameters may be too sensitive to voltage sag. 23 What can I do to protect against voltage “dips” Identify cost of protection vs. downtime losses Assess whole plant vs. individual equipment protection Work with equipment manufacturers to adjust tolerances Determine the source of the problem. Example, is the process control causing whole process to shut down? 24 Other Disturbances: transients, Surges, spikes Extremely fast voltage changes above the normal range lightning strikes equipment start-ups/ shutdowns capacitor switching operations 25 Solutions for Transients Surge Protectors Uninterruptible Power Supplies with built in Surge Suppression Isolation Transformer / Line reactors Constant Voltage Transformer 26 Surge Protectors- considerations Use in cascaded fashion for full protection One for the whole facility One at the sub-Panel One at point-of-use Installation Routing of conductors - shortest conductor length possible provides the most effective protection Rating Clamping Voltage Total Energy Dissipation UL 1449 2nd Edition 27 Define the Problem Conduct a thorough site investigation, which includes inspecting wiring and grounding systems. Pay extra attention to ground loops (do you have “illegal” bonds?) Establish a good understanding of the problem and its magnitude and what it is affecting. (UPS alarm may be beeping but no equipment is shutting off.) Monitor the incoming power for disturbances (monitor voltage and current) and at possibly the service entrance and at the affected equipment. Investigate equipment sensitivity to power disturbances (What can the equipment tolerate?). Determine the load disruption and consequential effects (Is a fraction HP drive tripping a whole production line?) Seek the help of people with experience rather than sales people. 28 Questions? 29
