Hydro Ltd. is the sole manufacturer of digital turbine governors for micro, small and medium capacity hydraulic turbines in Bulgaria. DTG–Hydro in its various modifications possesses all qualities of the modern digital turbine regulators on speed, and in some characteristics and unique technical solutions in the software surpasses many of the imported such systems.

Simplified digital turbine governor for MHPP

This design of ours solves the basic problem with complete automation of the private micro-HPPs with asynchronous generators that are built up en masse in this country nowadays, and it ensures the possibility these stations, exporting usually their power to the 20kV system, to work without operative staff. The simplified digital governor solves the following problems in the MHPP:

• Governing of unit speed for connecting in parallel with the system
• Automated unit loading
• Upper level control mode operation of the unit

Control and regulation are made on the basis of independent asynchronous software processes, supported by multi-problem system software. The principal processes are:

• Control of position sensors of the regulating apparatus of the turbine
• Control of speed and pressure sensors
• Control of exterior commands of operator from control panel
• Support of local console for control and commands
• Support of a communication channel using modems
• Support and activation of relevant discrete PID regulations

Operational functions of the simplified digital governor are:

• Preparation for parallel work and generating an impulse for switching on the unit circuit breaker to the system
• Transfer to turbine mode, automatic loading of the unit and transfer to automatic operation in upper level control mode.
• Normal stop of the unit
• Emergency shut down of the unit– under load or after load rejection
• Automatic re-starting – after external tension is restored, the unit starts and is switched on in parallel completely automatically without operative staff.

Practically the software of the governor controller solves all the rest technological problems, related to the complete automatic control of the relevant MHPP. The governor hardware is designed on the basis of industrial controllers of ABB of ‘Procontic’ newest series.

Digital turbine governor for small and medium HPP

This type of our digital turbine governors possess all characteristics and qualities of the modern digital turbine governors of the leading companies in this branch. It has been tested and found applicable for hydro turbines of Francis, Pelton and Mitchell-Banki type, coupled with synchronous generators and with capacities in the 750kW-15000kW range. In principle they consist of the following subsystems:

• Electro hydraulic system as a basic executive mechanism, consisting OPS with electric oil pumps and hydraulic control blocks
• Digital part, consisting of a basic programmable controller and auxiliary controllers, as the basic controller is an industrial product of ABB, Procontic type
• Primary sensors, registering the basic parameters of the unit, such as turns, electric power, position of the wicket gates or needles and deflectors, pipeline pressure etc.

DTG-Hydro possesses all basic functions, needed for the modern turbine governors as starting of the unit, synchronization, the normal and emergency shut down and power control in accordance with the preliminarily chosen operation mode. It automatically restores the revolutions of the unit after load rejection and ensures the possibility for a second switch on in parallel. In addition to the functions of the digital turbine governors, known by now, it can also make an economic distribution of the active power between the generators of a HPP or to participate in the secondary regulation frequency - exchange power.

The software, designed by Hydro Ltd., guarantees for the reliable operation of the generator in the following possible modes:

• Opening control mode
• Power control mode
• Level control mode
• Operation in accordance with static (speed/power droop) characteristic
• Operation in local greed
• Group control of the active power

DTG-Hydro in Stara Zagora HPP, investor NEC S.A. /2002/

In Stara Zagora HPP the hydro mechanical governor of U2, produced by CKD Blansko in the fifties, was totally rehabilitated by Hydro Ltd. in the beginning of 2002. The unit is equipped with a vertical Francis turbine 11550 кW at 750 min-1, directly coupled to the vertical synchronous generator. At principal’s demand, the existing OPS with working oil pressure 20 bar and the servomotors of the wicket gates were kept. Practically the entire control system of the existing governor was dismounted keeping the existing carter and the main hydraulic accelerator of the old governor. New electro hydraulic system of el. magnetic distributors and valves were installed. The digital part of the governor is placed in an electric cabinet with front service, installed in the machine hall. One of the last modifications of the ABB industrial controllers from the Procontic series – 07-KT-94 serves as basic controller.

Some of the technical characteristics of the governor are:

• Starting over governing - ≤ 5%;
• Speed deviation in no-load mode ≤ 0,1%;
• Active power deviation at constant static coefficient = 4,5% - ≤ 1%
• Static coefficient regulated within limits 0 ÷ 10%,
• External feeding voltage: 220 VDC
• Operating voltage for hydraulics 24 VDC