A problematics of implementation of power plant control systems to ensure its participation in an automatic secondary load-frequency control in the IPS of Ukraine

Automatic management of the TPP power reserves, which are allocated for secondary load-frequency control in the IPS of Ukraine is ensured through a modernization of the APCS of power units with simultaneous implementation of power plant control systems, with help of which a bidirectional data communication of MC of ALFCS of the IPS with power unit control systems of the power plants.

Analyzing a nature of requirements, which are applied to the implemented power plant control systems, we inevitably face difficulties in full satisfaction of requirements of the SE «NPC Ukrenergo» concerning an exchange of telemetering data. The full realization of completeness of exchange data on telemetering and telesignals are complicated for following reasons:

1. Simultaneously with the implementation of the power plant control system there is a necessity of technical re-equipment of existing TPP supervisory system, since the mandatory requirement of the SE «NPC Ukrenergo» is a necessity of gathering and quick transmission to a dispatch center of the SE «NPC Ukrenergo» (Kyiv) the full information on telemetering and telesignals from existing telecontrol of TPP. Transmission of this information can be ensured only in case of the modernization of the telecontrol system.
2. Necessity of modernization of the TPP telecontrol systems has long been relevant, because gathering and transmission of information from the OSGs about a current state of the switching equipment and the measured values of power, frequency, voltage, currents of electric mains are performed by means of the out-of-date and out of production telecontrol devices and transmit equipment, which use outdated data exchange protocols.

Existing means of TPP telecontrol do not meet modern requirements of gathering and transmission of data from telesignalization and telemetering. So, while gathering of the primary data of telemetering the physically and morally outdated analogue transducers of Е series are used. In the same time, the output circuits (5 mA level) from these sensors are connected with the existing telecontrol device via the cables with large lengths (more than 1000 m) that considerably affects accuracy of measurements. For data transfer on dispatch centers of the SE NPC Ukrenergo the physically and morally outdated transmit equipment (MKT-2, MKT-3, and TM-800) is used.  They do not allow carrying out a simultaneous two-way exchange of operational information. Further use of the existing communication protocol in the supervisory system is prevented by its limited address space, which is incorporated in this protocol, and also low data exchange rate (limited to 200 bps) that is unacceptable for the implementation of automatic secondary load-frequency control in the UPS of Ukraine. Transmission of information to the regional dispatch centers of the power systems is carried out with considerable delays which make up to 10-15 s, and sometimes much more, that leads to considerable decrease in accuracy at calculations in operative and information complex – OIC (as the data with different timestamp are taken in calculation). With such delays, dynamic error, due to receiving of late information, exceeds metrological error, so that accurate measurement of parameters becomes impossible. Furthermore, transmission of the required telemetering information to the MC ALFCS of the IPS of Ukraine, which is necessary to ensure managements of TPPs power units, is carried out with yet more delay as this transmission occurs through regional power system. The obvious there is that in the course of load-frequency control in the IPS of Ukraine these delays will cause an imbalance in the power system, lead to irrational changes of power flows and, as a consequence, contribute to origination of oscillatory process in the IPS of Ukraine; because the commands on change of an active-power of power unit(s) can be formed on the basis of the irrelevant data of telemetering due to considerable delay of their transmission in a situation when transmission time of control commands from the MC ALFCS to the APCS of power units via the PPCS will make up to 1-2 seconds with the subsequent working off of these commands by power units.

Technical requirements to the PPCS also determine that information exchange between the PPCS of TPP, MC ALFCS of the IPS of Ukraine (DC of the SE «NPC Ukrenergo») and DC of the regional PS should take place with a rate of 900-1200 bps for physical lines with mandatory use of standard international protocol IEC-870-5-101 (104). In order to ensure communications of the PPCS with DC of SE «NPC Ukrenergo» and DC of regional PS, it is necessary to provide 4 independent channels (2 channels for each DC, one among them – backup channel). Thus, the two existing communication channels remain to ensure communications with the existing telecontrol equipment of the TPP.

As a result of PPCS implementation without modernization of existing telecontrol of TPP, the requirement of the SE «NPC Ukrenergo», concerning a two-way exchange of the necessary information between the MC ALFCS of the IPS of Ukraine and the PPCS, are not fully ensured. In this case, the TPP obtains:

• ability to automatically control the power reserves of power units allocated for secondary control with ensuring of a qualitative exchange of the information, which is obtained only from modernized APCS of power units;
• information on a state of the OSG (telemetering and telesignals) from existing telecontrol, which will come to the PPCS with considerable delay in spite of the fact that between the PPCS and the MC ALFCS of the IPS of Ukraine will be ensured a modern  rate of data exchange;
• telemetry data transmission in the MC ALFCS of the IPS of Ukraine, which will come to a master controller from two sources: existing telecontrol and PPCS, and thus differences of data values will be inevitable, because necessary data from power unit’s systems will arrive much earlier, than from existing telecontrol.

Summing up the above said, the SE «Czechpol Energy» offers development and implementation of necessary measures on simultaneous implementation of the PPCS and technical re-equipment of telecontrol of power plants on the basis of creating a uniform software and hardware complex (SHC) that fully provide:

• improving the reliability of the TPP operation in the composition of the IPS of Ukraine at the expense of ensuring of effective participation of TPP’s power units in an automatic load-frequency control through connecting a power plant control system to a master controller of the ALFCS of the IPS of Ukraine with ensuring of all requirements of regulatory documents СОУ - Н ЕЕ ЯЕК 04.156:2009 and СОУ - Н ЕЕ 04.157:2009 relative to necessary data exchange rates and its completeness;
• creation on the PPCS basis of the united center of informational exchange between the MC ALFCS of the IPS of Ukraine, DC of regional PS of Ukraine, APCS of power units, DC of generating company (if any), remote users of a LAN of TPP;
• implementation of technical re-equipment of the TPP’s telecontrol based on software and hardware complex of PPCS;
• increasing possibility of surveillance over operation of power plant’s equipment for a power plant’s shiftman (in this case, the PPCS and telecontrol are considered as an united software and hardware complex, which functions in uniform time space);
• effective provision of TPP with auxiliary services, including with allowance for participations of TPPs power units in a tertiary control;
• implementation of monitoring system on providing of auxiliary services by TPP (regulation of frequency and power);
• implementation of the monitoring system for providing of auxiliary services by TPP (load-frequency control);
• Fast operative data gathering of telemetering and telesignalization and also state of switching devices 330, 220 and 110 kV;
• Output of telemetering information to the automated workstation (AWS) of the shift supervisor of TPP;
• gathering and transmission of the telemetering information on electricity production and its quality indicators, with the simultaneous considerable extension of its volume and the nomenclature of controlled parameters, to the dispatch center of regional PS of the SE «NPC Ukrenergo» and dispatching center of the SE «NPC Ukrenergo» using a new communications protocol;
• Saving the telemetering data, information on the participation of power units in load-frequency control in the IPS of Ukraine in the common archival database;
• Ability to use 4 channels instead of 6 (eliminates the need for 2-channels that are allocated for the existing telecontrol).
• Significant cost savings since a separate modernization of the TPP’s telecontrol will require:
• creation of software and hardware complex of telecontrol;
• preservation and output of telecontrol information on the separate workstation;
• ensuring the configuration and communication exchange of the telecontrol SHC with the PPCS.