Protection and Monitoring of SSEG systems MICROGRIDS Solar is the - - PowerPoint PPT Presentation

Smart remote control, Protection and Monitoring of SSEG systems

MICROGRIDS

 Solar is the fastest-growing renewable energy source in the world  More options than ever before for making the most out of their equipment

Smart Grid Development

Asset Management Can Be a Challenge

real-time and TOU When an energy system becomes too complex, it can cause a logistical nightmare for technicians and other grid managers.

Using smart storage to enhance solar performance

• Use stored energy to reduce energy drawn during peak times and to

support solar PV in the event of elements (eg cloud cover and rapid demand changes)

Control and Demand Side Management

MICROGRIDS

• Microgrids are a flexible solution for a broad diversity of stakeholders.
• The advantages of microgrids range from resilience to renewable

integration.

• Microgrids are moving from the laboratory to broad community

deployment.

• Microgrids still face significant legal and regulatory uncertainties.
• The ownership and business models of microgrids are still evolving.

MICROGRIDS

• A microgrid is not a single concept but rather a combination of technologies

and methods intended to modernize the existing grid in order to improve flexibility, availability, energy efficiency, and costs.

• Distributed energy resources (generation and storage) are fundamental parts.

They provide the necessary active characteristics to an otherwise passive grid.

• Advanced and distributed communications. All the grid components are able to
• communicate. The grid operates like a power-Internet (distributed, multiple-

redundant, interactive and autonomous). I.e. a Power-Net and Intelligent metering.

MICROGRIDS

Challenges of Microgrids are management, control and protection

Potential issues with microgrids integration into the main grid

• Stability: microgrids are variable loads with positive and negative

impedance (they can act to the grid as generators)

• Availability: Microgrids can trigger protections (directional relays)

upstream in the grid and interrupt service to other loads

• Safety: When there is a fault in the grid, power from the microgrid

into the grid should be interrupted (islanding)

MICROGRIDS

• Traditional over-current protection of LV networks will not be

applicable for LV microgrids with island operation capability

• Because high fault currents are not present during island operations,

new protection approach is needed

• Fast and selective operation is achieved by utilization of high-speed

communication

• Two main reasons for the speed requirements are stability and customer sensitivity

PROTECTION SYSTEM FOR MICROGRIDS

MICROGRIDS

• However, once islanding occurs, short circuit levels may drop

significantly due to the absence of strong utility grid

• In this case, protection system designed for high fault currents will

not respond and new protection strategies are required to ensure a safe islanding operation in a microgrid

• Current differential protection is proposed to detect and isolate the

feeder faults

Protection Issues

MICROGRIDS

• Microgrid source Controller: Uses local information to control the load/storage

relationship and needs to responds in milliseconds to changing events.

• Energy Manager: Optimizes individual microsources to meet power supplier

and customer needs by collecting system information and providing each microsource with its individual operating points (normally power and voltage set points

• Protection Coordinator: which rapidly isolates feeder faults within the

Microgrid and communicates feeder status changes to the Energy Manager.

Protection Communication and Control

MICROGRIDS

• One of the major challenges is a protection system for microgrid which must

respond to both main grid and microgrid faults

Protection Communication and Control

Adding microgrid features to a critical power grid creates protection challenges. 400

Mode of Operation Fault Location Fault current measured Grid without EG Main C/B 35.8kA EG in island mode EG C/B 8.96kA Grid with EG Main C/B 44.76kA

Comparison of Fault Current in different modes of operation

MICROGRIDS

• Large fault current magnitude variations
• TOC (time overcurrent) trip times increase when islanded – reduces microgrid

stability

• Could increase arc flash hazard
• Ground source issues
• Alternate relay settings may be required
• Fortunately, solutions exist

Challenges Summarized

MICROGRIDS

• Protect feeders and sources with differential elements
• Clear all faults at differential speed, islanded or grid-tied
• Collect sources on main bus
• Design dependable ground-source
• Group critical and non-critical loads
• Reduce arc flash hazards
• A dependable ground-source is needed during island operation

Thank You

Andre Anderson 0824749087 andre@energyneering.co.za