INTELLIGENT ELECTRONIC DEVICES INSTALLED IN AN ELECTRICAL POWER SYSTEM

DESCRIPTION Technical Field and Prior Art

The invention relates to a process of monitoring and/or configuring Intelligent Electronic Devices (IEDs) installed in an electrical power system.

Intelligent Electronic Devices are installed in electrical power systems, typically in an electricity generation, transmission, distribution, industrial or transport system. The IEDs are sited in electrical substations, and their purpose is to measure, protect, control and monitor the system to which they are connected. The topic of the invention refers to IEDs which protect the power system. So, these IEDs are also called "protection relays".

The figure 1 depicts an example of an electric power transmission system according to the prior art. The electric power transmission system comprises an overhead power line 1 and two sub-stations Si, S ₂ . Each sub-station S± (i=l, 2) houses an Intelligent Electronic Device IEDi. Each Intelligent Electronic Device IEDi is connected to the equipment of the sub-station Si and generates commands to control this equipment. A communication link 2, also referred as "teleprotection link", connects the two Intelligent Electronic Devices IEDi. The two Intelligent Electronic Devices IEDi (i=l, 2) and the teleprotection link 2 constitute a protection scheme intended to protect specific circuits of the electrical power system. The two Intelligent Electronic Devices IEDi (1=1 _/ 2) communicate with each other by means of the internal communication link 2. By receiving data from each end of the internal communication link, the protection scheme is better in discriminating whether any detected fault is within the protected circuit, or is outside of the relaying zone.

The protection relays require a degree of interaction with substation personnel from time to time. This includes monitoring and/or configuring actions to apply and control the relays (such as configuration, setting and testing) , to maintain and troubleshoot , to test the scheme periodically, to obtain protected circuit fault data, and to upgrade the resident software.

Different ways are known to operate the above mentioned actions.

Typically, such actions require that one or more personnel visit the substations at multiple terminals of the power system, which require significant travel time and cost in order to attend each substation.

The typical types of protection relays used in a geographically-dispersed teleprotection scheme operate on current differential or distance protection principles. It is typical that current differential relays provide a basic level of access to remote end relays. Such basic access typically includes: • The means to read current and voltage measurement values from the remote end(s), by means of continuous data communicated from the remote end ( s )

· The means to remove or reinstate one of the relay terminals from the scheme, for example to temporarily reconfigure a 3-ended differential scheme to a 2 terminal one

• The means to send binary commands and status information between the relays

It is also possible to obtain access remotely to substations by means of an existing communication channel to the substation. Plenty of digital substation control systems allow this. However this access is typically from a central location such as a national/regional control centre or a maintenance workstation, direct to a substation and the relays within it.

Alternatively, additional devices may be introduced into substations, in order to provide a link off-site to remotely-stationed personnel. Examples exist whereby 3G mobile links can be used to achieve such a connection, for example using virtual machine and remote desktop access type approaches. A problem is that additional equipment over and above the standard protection relay scheme needs to be added.

It is common also to have discrete teleprotection functions within substations, in which case data can be exchanged between substations. This data can include voice, status, binary commands (intertrips between circuit breakers at terminals, permissive or blocking signals) , file transfer, Ethernet traffic etc. The teleprotection link is provided by separate devices, outside of the protection relays .

In decentralised busbar protection schemes, it is possible to interact with bay (feeder) protection devices from the central unit in the scheme. However, these schemes are installed within a single substation (all equipment typically no more than 2km dispersed) .

Also, the IEC 61850-90-5 standard allows that a protection relay can communicate to another substation. However, it does not seek to propose ways that a user can use the communication channel for the purpose of configuration, setting and testing of remote devices.

All the prior art solutions require a dedicated communication connection which imposes additional equipment and therefore additional cost. The invention does not have such a drawback.

Description of the invention

Indeed, the invention relates to a process of monitoring and/or configuring at least one remote Intelligent Electronic Device located in a remote substation of an electrical power system, said remote Intelligent Electronic Device being linked by a teleprotection link with a local Intelligent Electronic Device located in a local substation, the local Intelligent Electronic Device, remote Intelligent Electronic Device and teleprotection link forming a protection scheme intended to protect specific circuits of the electrical power system, characterized in that the process comprises a step of implementing monitoring and/or configuring actions on said remote Intelligent Electronic Device from a software running on said local Intelligent Electronic Device, the data exchanged between the local Intelligent Electronic Device and the remote Intelligent Electronic Device when running the software being transmitted through the teleprotection link .

According to another feature of the invention, a monitoring and/or configuring action is to perform a software upgrade of said remote Intelligent Electronic Device from said local Intelligent Electronic Device.

According to yet another feature of the invention, a monitoring and/or configuring action is to get power system data stored in said remote Intelligent Electronic Device and to send said power system data to said local Intelligent Electronic Device.

According to yet another feature of the invention, a monitoring and/or configuring action is to set said remote Intelligent Electronic Device by means of application settings coming from said local Intelligent Electronic Device.

According to yet another feature of the invention, a monitoring and/or configuring action is to extract setting files from said remote Intelligent Electronic Device and to send the extracted setting files to said local Intelligent Electronic Device, or vice-versa, from said local Intelligent Electronic Device to said remote Intelligent Electronic Device. According to yet another feature of the invention, a monitoring and/or configuring action is to indicate to said local Intelligent Electronic Device an indicative real-time usability statistic of said teleprotection link.

According to yet another feature of the invention, a monitoring and/or configuring action is to send test data to the remote Intelligent Electronic Device from said local Intelligent Electronic Device, such that some testing actions are prepared and initiated for said remote Intelligent Electronic Device .

According to yet another feature of the invention, testing actions simulate a fault condition at said remote Intelligent Electronic Device.

According to yet another feature of the invention, a monitoring and/or configuring action is to offer the ability for a user to operate the protection scheme in a degraded mode if the teleprotection link has a low bandwidth and a greater proportion of the available bandwidth is needed in order to allow said remote and/or local Intelligent Electronic Device access tunnelling at an acceptable level of performances .

Advantageously, the process of the invention proposes to use the teleprotection link between the IEDs to start the maintenance actions relating to all or part of the IEDs of the power system from a single IED of the system.

The interaction with remote terminal relays is achieved by means of using any available bandwidth of the teleprotection link between the relays. This approach is particularly useful as in many cases there is no reliable telecommunications link to the substation other than the teleprotection link between the IEDs.

By the fact that the teleprotection link has a mission-critical task on the power system, the teleprotection link is fast, dependable and secure. Thus, where communication bandwidth remains, this link is well-suited to support personnel interaction with remote terminal relays. The personnel (typically field technicians/engineers) would effectively access a relay at one local end, and the relays in the scheme have the intelligence to manage a "tunnel" to the remote end relay to which access is required.

Brief description of the figures

Other characteristic and advantages of the invention will become clearer upon reading a preferred embodiment made in reference to the attached figures among which:

- Figure 1 depicts an example of an electric power transmission system according to the prior art; and

- Figure 2 depicts an example of an electric power transmission system according to the invention.

Detailed description of a preferred embodiment

The figure 2 depicts an example of an electric power transmission system according to the invention . According to the invention, a computer 3 is linked to the Intelligent Electronic Device Si of the electric power system. The computer 3 contains a software able to address the different IEDs so as to activate the maintenance programs of the these IEDs. The way data coming from the computer 3 reaches the different IEDs is via the communication link 2, accessed through the Intelligent Electronic Device Si. First, this requires that an authorised technician/engineer makes a connection with the protection relay Si at the local end, typically by "logging-on" with a software loaded in the computer 3 . Indeed, there is the need to authenticate the user to check her/his authorisation to perform this log-on.

In prior art solutions, the user performs commissioning, test and maintenance actions for the local relay only, plus, in some cases, the few limited actions mentioned above (cf. the basic level of access to remote end relays mentioned in pages 2-3) .

According to the invention, the user performs commissioning, test and maintenance actions for any remote relay connected to the local relay using the teleprotection link between the IEDs. The software which implements the process of the invention is mainly resident in the software loaded in the local Intelligent Electronic Device IEDi. Indeed, the software loaded in the leal Intelligent Electronic Device IEDi knows the data relating to the configuration and the availability of the communication link 2, which data are used for implementing the process of the invention. The computer 3 is used to control the software loaded in the local Intelligent Electronic Device .

Specifically, the process of the invention includes all or part of the following steps:

1) Indicating to the user an indicative real-time usability statistic for the teleprotection channel to each remote end, should they decide to use it to tunnel access to the relays at that/those end ( s ) ,

2) operating the protection scheme in a degraded (economised) mode (lesser or slower performance) if the teleprotection channel has low bandwidth and a greater proportion of the available bandwidth is needed in order to allow the remote end access tunnelling at an acceptable level of performance,

3) performing a software upgrade of the remote end protection relay (s) from the local end relay,

4) sending device application settings to the remote end relay (s) - these are the protection element thresholds and other configuration settings which are used to "set" the protection relay ready for its task,

5) extracting setting files from remote end relays, for instances where the user wishes to obtain the as-fitted status at the remote end (typically for analysis, or to make a clone copy at the local end) ,

6) getting sampled waveform records (stored power system data, often termed as "disturbance records" or "oscillograms") from the remote end(s), and making them available for saving to the user' s computer at the local end,

7) sending test data over the communication link, such that testing actions can be prepared and initiated for the remote end(s) (this could, for example, include the sending of a waveform file to apply as a simulated fault condition at the remote end ( s ) ) .

At the completion of work, the user would then need to return the scheme to normal, by secure log-off, or a time-out if they fail to do it.

Related to some of the points 1)-1) mentioned above, it is possible to make the following remarks :

Point 1)

The usability statistic would typically be shown as a speed percentage for interactions with the remote end relay (s), compared to "100%" speed which would be the nominal full speed interaction rate available for the same interactions with the local relay .

Point 2)

There are instances when the advantages of not having to travel tens or hundreds of kilometers to a remote end substation ( s ) far outweigh keeping the protection scheme operating at the highest performance over the teleprotect ion channel. In such instances, it may be possible to run the protection scheme more slowly or less frequently, in order to free-up bandwidth for the remote tunnelling. When there is an "outage" of the circuit, this means that the circuit is electrically dead, with the circuit breakers open at all ends (terminals) of the circuit, meaning that protection is not required. If there is not an outage, but the personnel know that other protection relays are correctly protecting the circuit, it may be acceptable to temporarily run in slower-speed mode.

Point 3)

Upgrading of the remote end software: This would involve transferring a large amount of data but would be done whilst the protection was out of service so the full bandwidth available from the teleprotection link would be used. Additionally the upgrade scheme would ensure that all settings were retained and restored after the upgrade, with a method employed such that if the upgrade failed the existing software would be automatically restored.

Point 4)

A technique will be designed such that if the link fails during transfer of settings the remote relay restores the previous settings.

Point 7)

There are two options available for this. One method is that a file containing test waveform sampled data (termed typically as a COMTRADE file) can be transferred via the link to the remote relay' s memory and applied to that relay only as a single-ended virtual test, invoked from the local end. Additionally, the second method allows a suitable COMTRADE file to be loaded directly into the local relay memory and also via the link into the remote relay (s)' memory (ies). Then using IEEE1588 (or another equivalent precision-time protocol) to ensure synchronisation of the relays' internal clocks, all relays can be configured to apply the test simultaneously, invoking the test at a predetermined, synchronised instant at all ends.

A big advantage of the process of the invention is that commissioning, maintenance, test and troubleshooting actions in relation to all the IEDs connected in a same protection scheme can be done from only one IED of just one substation via the teleprotection link between the IEDs.

Visiting site is costly in terms of travel, and the time of the visiting technician/engineer, but also there are issues of site security and access, and supervision of the work. In addition, the protection scheme will often need to be taken out of service for the duration of the work, which traditionally included the personnel travel time between all ends of the protection scheme. By removing the need to travel between the ends, and perform the work from one end/terminal alone, the protection scheme downtime is greatly reduced.