Network A interconnected with network B and sharing generation surplus

What are Network Interconnections

Grid Interconnections are found between:

• Two or more regions
• Two or more utilities within a region
• Two or more states or countries

Where one region will have generation surplus and other region may have generation shortfall – interconnecting maintains stability of both the regions

What is the need & growth of Network Interconnection

• Interconnecting two or more separate power systems improves stability in each system by helping the other balance generation and load.
• Both systems are now able to share generation and help the other serve load if they experience a generation shortfall.
• Another benefit of interconnection is to take advantage of lower cost generation sources.
• Renewable Energy projects are triggering more inter-connections.

GE's SIPS approach

GE offers two approaches for reducing instabilities and overloads on interconnected networks to provide safety and reliability to these networks. These approaches may be combined or used separately.

• Contingency action solutions
• Detection and dampening of system oscillations

What are customer challenges & customer objectives with respect to Network Interconnection

Intelligent monitoring devices put across the networks connected
centrally to GridNode controller to execute contingency actions

GE's contingency action solution detects a disturbance in one part of an interconnected network which could result in interconnection overloading or frequency and voltage stability conditions. GE’s solution will take action to remediate these situations by stabilizing the load and generation on the networks thereby protecting the interconnect.

Contingency Action Solutions

• Detect major changes in any of the connected networks (faults)
• Measure overload in interconnect and associated voltage and frequency changes
• Shed load to reduce load on interconnect
• Drop generation to reduce overvoltage
• Trip the interconnect
• Balancing the two networks

Key Characteristics

• Millisecond response time (typically under 250ms)
• Supports existing protection and metering devices and protocols
• Can support complex network topologies (i.e., mesh grids)
• Provide advanced notice of interconnection trip to operators
• Available customized HMI

PMU's detecting oscillations are installed across the networks connected
centrally to GridNode Controller to trigger dampening actions

System oscillations* across an interconnect are caused by a major change (fault) in the connected networks and the associated sources are attempting to compensate to balance the load and generation. If oscillations persist local protections within a network will react to protect the asset and trip the generators offline.

Using synchrophasor, GE's system oscillation remediation solution detects network oscillations and determines if these will heal itself. When it is determined these oscillations will not heal itself, GE's solution will attempt to dampen the oscillations and if needed trip the interconnect.

Detection and dampening of system oscillations

• Detect prolonged/growing interconnect oscillations
• Trigger network damping circuits such as Power System Stabilizers (PSS) to dampen oscillations
• Temporary shed load to dampen large oscillations
• Temporary drop generation to dampen large oscillations
• Trip the interconnect

Key Characteristics

• Millisecond to second response time
• High speed situational awareness using synchrophasor
• Can support complex network topologies (i.e., mesh grids)
• Provide advanced notice of interconnection trip to operators
• Available customized HMI

*Both system (natural) and forced oscillations

Measurement Equipment

Contingency action solution

• Protection Relays, Meters
• Protocols: DNP3, IEC 101/103, Modbus, RGOOSE/GOOSE, Synchrophasor C37.118-1, 61850

Detection and dampening of system oscillations

• Phasor Measurement Units
• Protection Relays with PMU capability
• Synchrophasor C37.118-1 protocol

Communications Equipment

Within a substation

• Ethernet switches
• Media/Protocol converters

Wide Area communications

• SONET multiplexers
• Ethernet backbone
• Wireless radios

Example of interconnection between the grids using Oscillation Detection

• First of its interconnect between European grid which had a strong source and a Turkish grid which had a weak source.
• Due to these differences in the sources any major disturbance in the network will be slow to stabilize resulting in oscillations across the interconnect.

GE's oscillation detection solution monitors the active power flow between Turkey and Bulgaria/Greece.

Upon detection of the oscillation, GE solution will shed up to 1400MW of load across 15 substations located in Istanbul region to dampen the oscillations.

*European Network of Transmission System Operators for Electricity