Systems for the supervision, management and remote control of the Distribution Network

Pursuant to Law 4001/2011, the basic mission of HEDNO is the operation, maintenance and development of the Electricity Distribution Network and the management of the electrical systems of the non-interconnected islands under favourable economic conditions.

HEDNO seeks to perform the above operations by up-to-date and efficient means, relying more and more on “smart” networks, extensive automation, remote metering data on consumption and remote customer support services, while adapting to all new developments in the industry of electricity.

In general, by upgrading our facilities and working methods, we also seek to fulfil the Company’s main objectives, namely:

improving the quality of energy and its services

the gradual reduction of costs

actively contributing to the efficient operation of the electricity market

the protection of the environment

HEDNO is in the process of upgrading the entire network by procuring and installing new remotely controlled equipment, which consists of:

In addition to the 2 SCADA / DMS modern systems HEDNO has made available in the Islands Region and in Attica, it is now in the process of replacing the existing 8 SCADA / DMS systems with 3 new equivalent systems in its remaining 3 Regions, i.e. in the Region of Macedonia-Thrace, the Region of Central Greece and the Region of Peloponnese-Epirus.

The 3 new SCADA Control Systems will ensure:

Reliable operation and reduction in human resources necessary to support and maintain them.

The lifespan and support for hardware and software (at least 15 years).

Reduced operating costs due to maintaining newer and more modern equipment.

Increased flexibility in communication and interconnection with both existing and future new equipment (Remote Control Load Switches, Auto Reset Switches, Fault Passage Indicators, and Small Terminal Control Units for Medium Voltage Substations).

DMS (Distribution Management System) applications will offer a modern environment for:

Calculating load flows
Identifying optimal cross sections of the flow of MV network, aiming at minimizing energy losses and optimizing the supply of electricity to consumers.
Real time Load Allocation and State Estimation.
Predicting loads.
Better management of voltage levels across the network.

The combination of the new SCADA systems with DMS applications will also allow for multiple indirect benefits such as:

Improving energy quality indicators (SAIDI, SAIFI, etc.)

Reducing damage to equipment

Better use of existing staff

Reducing energy loss due to technical failure

Possibility of exchanging data with other systems, such as:

The GIS (Geographical Imaging) system of the Network.
Web applications for data presentation.
Call Center and IVR for real-time updating of Network Users on the time required for resuming supply after power outage or scheduled power cut.

At the same time, HEDNO is planning to establish 5 Central Regional Distribution and Control Centers (RDCC) in order to replace 57 local RDCCs currently in operation.

The operation of Regional RDCCs and the integration of all High Voltage Substations into SCADA systems will ensure:

The prevention of damage to fixed assets under HEDNO’s jurisdiction by identifying in good time:

Serious damage to computers, such as loss of protection circuits.
Overloading of Power Transformers and MV Lines.

Safer distribution network operation with timely tracking of:

Voltage fluctuations on busbars.
High leakage from HV/MV Transformer Hub.

Reducing operation costs by:

Saving on human resources that are necessary for staffing and operating old local RDCCs.
Running maintenance work on a reduced number of terminal equipment.
Dynamic display of the state of MV Network.
Monitoring remotely controlled items and their effect on the Network they feed.
Dynamic monitoring of the MV network and real-time fault display.

The modern tendency to improve energy quality indicators necessitates the automation of the MV network through remote control and monitoring of the installed equipment.

In this context, within the next years HEDNO is going to acquire and install a significant number of remotely-controlled load switches and remotely-controlled Automatic Reset Switches in the overhead MV network. The installation of these Switches will result in:

Benefits in network operation:

Improvement of the quality index of electricity supply (e.g. SAIDI, SAIFI etc.) through the automatic operation of the switches in question as well as by remote control and remote monitoring in the MV network.

Network supply safety due to discharge of loads (e.g. irrigation loads) to address critical system conditions (e.g., failure to cover load due to power production shortage).

Improved network protection.

Improved quality of voltage management across networks.

Reduced energy losses due to better network management.

Improved network monitoring with information made available from remote surveillance systems with more secure and more efficient network operation as a result.

Benefits in terms of performance:

Reduced HEDNO operational costs, due to better utilization of existing human resources (e.g. limiting the deployment of employees to on-site operations).

Reduced energy loss due to faster network fault detection and reduced technical losses.

Reduced stress on the components of the MV network during network resetting following outage due to fault.

Reduced risk of damage to important and expensive HV and MV Substation equipment.

Utilizing the new SCADA systems further.

Company staff shall acquire technical know-how through the use of new systems.

As mentioned above, the modern trend towards improving energy quality indicators necessitates the automation of the MV network. In underground MV networks, automation includes:

MV switchgear remote control

Remote monitoring of installed equipment (load switches, underground cables, metering equipment, safety equipment).

Appropriate Remote Terminal Units (RTUs) are used for the above operations. RTUs are installed on MV/HV Substations and are suitable for:

Remote control of the installed load switches by the appropriate Network Management Center with simultaneous monitoring of their condition

Monitoring the condition of other Substation equipment

Short Circuit Current Recognition (fault passage indicator mode)

Receiving power measurements from underground cable lines and transmitting them to the appropriate control center

Receiving voltage measurements

Communication between RTU for automated execution of operations to isolate a fault in the underground network or in combination with a DMS (Distribution Management System) for reorganizing the network in order to reduce technical loss without causing a nuisance to network users.

Due to their multiple capabilities, the installation of Remote Control Units is useful because it:

Reduces the necessary time for repowering customers after an outage or scheduled work which results in improving the performance indicators in supplying electricity to network users (SAIDI, SAIFI, etc.)

Carries out network redeployments (supplying network users from a different point in the network in order to reduce their technical losses and strain on their components (conductors, switches, etc.)

The usual results of the above are as follows:

Compliance with the rules set by the Regulatory Authority for Energy (Regulatory Decision)

Reduced cost of Undistributed Energy. The cost of Non-Distributed Energy is the cost incurred in the National Economy [€/kWh] for each kWh demanded by consumption which cannot be disposed by the Network

Reduced amount of investment to improve the Network.

HEDNO is carrying out the installation of a significant number of Remote Control Units in MV/HV Substations after conducting a study in order to identify the Substations in which installing these units will have the optimal technical and economical result.

As mentioned above, one of the major goals of any Electricity Distribution Network Operator is to improve the quality of the energy supply, which is assessed by improving the SAIDI and SAIFI quality indicators.

Improvement of these quality indicators is achieved at comparatively small costs, by reducing the time to track failures in the Medium Voltage (MT) network through the use of Fault Passage Indicators. These devices are installed at appropriate locations on the overhead and underground MV networks and provide local or remote readings in the event of a short circuit current passing through.

Despite the simplicity of the idea, it has proven to be a cost-effective solution in improving the distribution network’s reliability. Many studies have linked the development of Fault Passage Indicators technology with significantly improved SAIDI and SAIFI quality indicators.

In particular:

Improved SAIDI: Improvement is proportional to the number of Fault Passage Indicators installed and the degree of prior existing network automation.

Improved SAIFI: By using Fault Passage Indicators, we avoid identifying the fault point trough successive electrification trials in fault conditions, a practice that puts strain on network components (cables, coupling and protection devices, insulators, etc.) resulting in reduced life span and an increase in the number of fault passages (increased SAIFI).

In the event of a fault passage, the reading is provided:

Locally: For example, if a Fault Passage Indicator is installed on a MV/HV Substation indoors (Substation inside a building), a local light indicator lights up (e.g. on the façade of the building housing the Substation) so that the technical crew may locate the point of failure easily.

Remotely: New technology Fault Passage Indicators transmit fault detection results through a telecommunications network to the local RDCCs. The use of Fault Passage Indicators with telecommunication leads to an even greater increase in network reliability, by reducing the time needed to locate the point of the fault further.

On the basis of the above, it is concluded that the installation of Fault Passage Indicators, apart from improving the SAIDI and SAIFI quality indicators and ensuring compliance with the relevant regulations set by the Regulatory Authority for Energy (Regulatory Decision), can also give rise to considerable financial benefits, i.e. a decrease in the cost of Undistributed Energy and a decrease in the level of investments required for network improvement as mentioned with regard to MV/HV Substation Control Units (MV underground Substation network).