1 IEEE1818-2017 Guide for the Design of Low Voltage AC and DC Auxiliary Systems for Substations Sponsored by the IEEE Substations Committee Presented By Joe Gravelle
Organization of the Guide 1. Scope / Purpose 2. Normative References 3. Definitions 4. AC System Design 5. DC System Design Annex A Bibliography Annex B - Conductor Sizing examples Annex C Battery Sizing Examples 2
Organization of the Guide 1. Scope / Purpose 2. Normative References 3. Definitions 4. AC System Design 5. DC System Design Annex A Bibliography Annex B - Conductor Sizing examples Annex C Battery Sizing Examples 3
1.1 Scope This guide provides guidelines for the design of the ac and dc systems. This guide covers the low voltage auxiliary systems from the source(s) to the distribution point(s). Reliability requirements and load characteristics 4
1.2 Purpose The low-voltage ac and dc auxiliary systems comprise very important parts of the substation equipment. Design of the ac and dc auxiliary systems reliability, load requirements, system configuration, personnel safety, safe and reliable operation protection 5
6 2.0 Normative References IEEE 485, IEEE 525 3.0 Definitions Definitions are provided for technical terms used in the guide.
Organization of the Guide 1. Scope / Purpose 2. Normative References 3. Definitions 4. AC System Design 5. DC System Design Annex A Bibliography Annex B - AC examples Annex C DC Examples 7
4.0 AC System Design Design Criteria Source Requirements Load Analysis Conductor Selection Transformer(s) Transfer Switch Bus Layout Panels Protection Equipment Specifications Operations and Maintenance 8
9 4.1 Introduction Design Criteria Source Requirements Number of sources 1 phase or 3 phase Load Requirements These sections define the AC system for the substation Application.
10 4.2 Design Criteria AC system loads 1 or 3 phase System stability Protection Voltage This section defines the AC system design.
11 4.3 AC sources Transformer tertiary Substation bus Distribution line Generators
12 4.4 AC Load Analysis Identification Amps/Volts/kW Equipment rating Demand factors Load calculations
13 4.5 Conductor Selection Conductor Type Insulation Temperature Rating Size Ampacity Voltage Drop
14 4.6 Station Auxiliary Transformer Transformer Type
15 4.6 Station Auxiliary Transformer Number of transformers Single/Three phase Transformer Ratings Transformer Connections
16 4.6 Station Auxiliary Transformer Transformer Ratings KVA Voltage Short Circuit Impedance BIL
4.6 AC System Design Transformer Connections Single Phase 17
18 4.6 AC System Design Transformer Connections Three Phase
19 4.7 Transfer Switch Manual / Automatic Considerations: Break before Make Switching Neutrals
20 4.8 Bus Layout - Distribution Configuration Essential / Non-Essential Loads Simple Radial System Expanded Radial System Primary / Secondary Selective systems
21 4.8 Bus Layout and Distribution Circuit Configuration
22 4.9 AC Distribution Panelboards Application Ratings Short Circuit ratings Standards
23 4.10 AC Auxiliary System Protection Panelboard or Switchboard Circuit Breaker Selection Fuse Selection
24 4.11 Equipment Specifications General considerations Standards
25 4.12 Operation - Maintenance Consideration Accessible Disconnects Indoor/Outdoor Design Adequate Working Space Standby or Backup AC System
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Organization of the Guide 1. Scope / Purpose 2. Normative References 3. Definitions 4. AC System Design 5. DC System Design Annex A Bibliography Annex B - AC examples Annex C DC Examples 27
DC System Design Design Criteria DC Equipment One Line Diagram Batteries Chargers Panels Design Considerations Maintenance Provisions 28
Battery System 29
30 Battery System Single cell battery with acid containment on a two step rack
31 5.1 DC System Design Criteria Reliability Redundancy Environment
5.2 Equipment Served by the DC System System Protection Equipment Motor Operators Breakers SCADA Fire Protection Security 32
5.3 One Line Diagram Power System One Line System protection DC System One Line DC Load Calculations DC Connections Number of Batteries Load Transfer 33
34 Substation One Line Operating sequence: 12D3 is normally closed, no generation on feeder circuits Operating time for MOS 10 seconds Transformer T1 differential: Trip 69CB1, 69CB3, 12CB1 Open 69DT1 Breaker Failure on 12CB1: Open 12CB2, Open 12D3, Reclose 12CB2
35 DC System Battery To DC Cab. Panel Maint Charger & Battery Battery Charger
DC System distribution cabinet(s) 36
37 5.4 DC Batteries Battery System Battery Charger(s) Battery Disconnect(s) DC Panel(s) Maintenance Connections DC Loads
5.4 DC Batteries 38
39 5.4 DC Battery Types Vented Lead Acid (VLA) Valve Regulated Lead Acid (VRLA) Nickel Cadmium (NiCad) For substation use, vented lead-acid cells are the most common
5.4 DC Battery 40
5.4 DC Battery 41
5.4 DC Battery 42
43 Battery Sizing Sizing the battery using IEEE 485 (Vented Lead Acid Batteries) Defining the Duty Cycle (loading on battery based on time duration) Continuous Load Momentary Load Worst Case Tripping
44 Continuous Loads Indicating lamps, Microprocessor Relays, Electronic Meters, SCADA Systems, Annunciators, Communication Equipment o For loads that are non-linear such as power supplies, the current increases as voltage declines. o The watt rating is typically used to determine current at end of battery cycle discharge voltage
45 Momentary Loads Lock Out Relay (LOR) Breaker tripping Motor Operators Breaker Fail operation Considerations: o Worst Case Tripping Scenarios o MOD use Locked Rotor rating o Breaker Fail use SOE not sum of all currents select highest
46 Worst Case Tripping Operating sequence: 12D3 is normally closed, no generation on feeder circuits Operating time for MOS 10 seconds Transformer T1 differential: Trip 69CB1, 69CB3, 12CB1 Open 69DT1 Breaker Failure on 12CB1: Open 12CB2, Open 12D3, Reclose 12CB2 Timing: T=0cy (0 sec) Trip 69CB1, 69CB3, 12CB1, open 69DT1 Current=12+12+8+60=92A T=12cy (0.2sec) (12CB1 breaker failure timer) Trip 12CB2, Re-Trip 12CB1 open 12D3 Current=20+8+8+60=96A T=600cy (10sec) Reclose 12CB2 Current=6A From the above, the worst case tripping load is 96A for the 12CB1 breaker failure.
47 Duty Cycle Duration 1. Charger fails Initiates Alarm to SCADA 2. Dispatcher notices Alarm 3. Dispatch contacts Substation Personal 4. Substation Personal Drive to Substation 5. Investigate Alarm 6. Determines Charger Failed contacts dispatch requesting maintenance 7. Dispatch contacts Maintenance 8. Maintenance Technician Drives to Substation 9. Maintenance attempts to repair charger (unsuccessful) 10. Maintenance Supervisor locates spare charger 11. Maintenance Supervisor contacts additional resources 12. Resources drive to service center PU spare charger and drive to substation 13. Replace failed Charger
Duty Cycle Example 48
49 Battery Chargers Sizing battery Chargers Charger Connections Charger Circuit Protection
Battery Chargers 50
Battery Charger size 51
52 DC Panels Considerations Critical Loads vs non-critical Loads Circuit size Number of circuits
DC Panels 53
DC Panels 54
55 Design Considerations Battery location Maintenance considerations Working clearances Method for removing battery cells An eyewash station Spill containment systems Terminal Covers
Battery Terminal Covers 56
57 Design Considerations Battery area temperature Specifications published for sizing Heat and Cold impact battery performance Reference IEEE485 for effect on Battery Size
Design Considerations Acid spill containment Spill Pans Acid-resistant paint on the floor 58
59 Design Considerations Battery racks Three types step, tier, or stepped tier Height variations between cells can cause cell temperature differences within the same battery system acid-resistant coating applied to the structural frame seismic zone
60 Design Considerations Battery rack
61 Design Considerations Circuit considerations Grounded and ungrounded systems Ungrounded Substation Control - SCADA Grounded ((+) grounded) Communications
Design Considerations - Circuit considerations Isolation of Main DC cables Recommendations - IEEE 1375 Battery fuse Battery circuit breaker Battery disconnect switch Mid-point battery fuse 62
63 Circuit considerations Isolation of main dc cables - Separate the pos and neg cables
64 Design Considerations Circuit considerations Coordination of overcurrent protection Short-circuit levels Fuses Breakers Equipment voltage ratings
65 Maintenance Provisions Isolation switches Equipment accessibility Back-up supplies
66 Maintenance Provisions Testing Provisions
67 DC System Battery To DC Cab. Panel Maint Charger & Battery Battery Charger
68 Annex Annex A Bibliography Annex B - Conductor Sizing Example Annex C Battery Sizing Example
Questions? 69