Vattenfall Wasserkraft GmbH (VWK) operates the Hohenwarte II pumped storage power plant (PSW Hoh II) on the upper reaches of the Saale in the district of Saalfeld-Rudolstadt. In the period 1963 - 1966, eight pumped storage units (PSS) were put into operation in this power plant, which have the following technical data:
Rated power motor-generator 50 MVA
Nominal power turbine operation 40 MW
Nominal capacity pumping operation 42 MW
Nominal voltage 10.5 kV
Nominal speed 428.6 min-1
Durchgangsdrehzahl 700 min-1
Mass rotating part 135 t (motor-generator) + 34 t (turbine) + 28 t (storage pump)
Schwungmoment 860 tm²
Outer diameter brake track 2,850 mm
Width of braking track 300 mm
Below the generator stand is the lower support star. On the arms of this support star there are four oil-hydraulically actuated, single-acting brake cylinders with piston return springs. Mechanical braking is carried out by hydraulic pressing of brake pads to the brake track on the generator rotor.
This mechanical braking device is used to shorten the run-out phase of the rotating part of the PSS. The motor-generator is electrically braked during normal operation, so the mechanical brake mainly works as a standstill brake. Only in the event of failure or prohibition of electric braking is it used for rapid stopping. It is also used to lift the generator rotor during repair and maintenance work.
The subject of the tender is the dismantling and disposal of the mechanical braking and lifting systems as well as the design, manufacture, delivery, installation and commissioning of new mechanical brake systems on all eight PSS in identical design.
The first conversion of a braking system is to take place as part of the interim revision of the PSS C, which is planned from 07.08.2023 to 26.04.2024 (date adjustments on the part of the AG are possible).
The other seven conversions are to be carried out as part of further call-offs (options) within the framework of subsequent, planned shutdowns. In order to enable both effective work planning by the contractor and long-term downtime planning by the client, the offer must be accompanied by information in accordance with the annex "Brake system renewal specifications".
Scope of services: The oil lines previously used for the hydraulic brake system, including the valves up to the combination valve block Mg31c (P3 % 3MEX00 AA602 and P3 % 3MLA40 AA751), are to be dismantled and handed over to the client for disposal, the flanges/openings are to be closed professionally, the four brake blocks of the first conversion lot are to be carefully removed and handed over to the client for possible further use (their refurbishment is not part of this scope of services), for the other conversion lots, the dismantled brake blocks are handed over to the client for disposal.
The existing manually operated oil unit for lifting the pole wheel is to be integrated into the new piping, as it is to be used for safety measures (applying the brakes during longer standstills without existing pressure from the DÖR).
Four double-acting brake blocks are to be supplied and installed at the previous assembly stations, which are supplied with oil pressure (20 bar ± 15 %) via two ring lines on the "brakes applied" side or the "brakes filed" side.
The oil pressure is provided at the DÖR pressure oil unit (P3 % 3MXH00 BB002) (the exact interfaces are to be suggested by the contractor, from there new lines to the brake blocks are to be supplied and installed. In terms of circumference, the ring lines can be dismantled and reassembled as quarters by means of "whale shape + screw connection". From this ring line circuit, screwable cable sections of easily manageable length must be provided. Up to the associated oil reservoir, a leakage oil line and a drain line must be relaid from both pressurized sides, including shut-off valves (corresponding to fittings P3 % 3MLA40 AA401) in order to be able to carry out safety measures on the hydraulic system. The lengths of the individual lines are to be measured by the contractor in each case, for calculation purposes approx. 40 m can be used each.
A solenoid valve is used to control the brake system (suitable for permanently available coil voltage 220 V DC +15/-20 %, exact type must be coordinated with AG). This solenoid valve is mounted on the pressurized oil unit. The electrical connection of the solenoid valve is carried out by the AG. In order to establish the safety measures (shutting off the brake system, draining/depressurization), appropriate fittings must be provided at the point of supply (pressurized oil unit).
Displacement sensors (preferably TURCK Ni50-Q80-LiU-H1141 with 24 VDC control voltage) are to be installed on the new brake blocks, which map the entire travel as a 4...20 mA signal and make it available to the process control system (the four sensors per brake system are connected by AG).
The brake blocks must be equipped with brake pads (asbestos- and metal-free, preferably STS Friction GmbH, type STS2010 or equivalent) riveted to suitable steel plates. When the wear limit is reached (please specify), it should be possible to replace these carrier plates with the worn brake pads due to the confined installation space by loosening a few (secured) screw connections.
All screw connections used in the interior of the motor-generator must be secured against loosening (preferably Nord-Lock washers, alternatively locking washers with foldable lugs). The new braking system must be designed in such a way that the braking effect achieved does not exceed the previous braking times.