scope:

Purpose and Scope of Guideline

The present Part 1 of the Guideline VDI/VDE 3521 Covers steam turbine governing systems for the individual controlled variables, viz. speed, frequency, power, and pressure (initial pressure or back pressure), where the position of the steam admission valves is the only manipulated variable. Included are those operating modes of the turbine where two output variables, e. g. frequency and load, are controlled in common in a fixed functional relationship to each other, as well as operating modes where a variable characterizing the driven machine (e. g. delivery head, flow rate) forms the controlled variable. Thus the Guideline is applicable to turbines driving generators operating in synchronism with a grid system and general driven machinery (including generators which are not tied to a grid).

The present Part 1 indicates straightforward methods of testing which essentially enable the static Performance of the steam turbine governing system to be determined in conjunction with the turboset. For this purpose, the principal static characteristics of the governing system are defined on the basis of the definitions in DIN 19226, Edition 5/68 and illustrated by graphs. Practical methods of testing are then described to determine the characteristic relationships of a number of typical operating modes of the turbine - each separately defined and illustrated by a control diagram. Comments on preconditions, measuring methods and documentation of the test complete this part of the Guideline.

The testing of the dynamic properties of turbine control systems in this part of the Guideline is limited to establishing the time response of individual components of the governing system by means of selected test signals in preparation of further tests according to Part 4 of the Guideline series. The overspeed behaviour of the turbine may be tested according to Part 2. Governing systems responding to several variables (e. g. on extraction turbines) are dealt with in Part 3. Part 4 finally Covers the testing of the dynamic behaviour of the complete plant as a closed control loop in matching power output to system demand as well as evaluation of the test results for the quality of control obtained. The definitions, procedures, evaluation methods and quality criteria to be applied in evaluating the tests are laid down in the relevant parts of the Guideline dealing with the particular aspect.

The Instructions and procedures compiled in this Guideline represent recommendations according to which the practical testing of steam turbine governing systems can be carried out. Reference is made to the procedures in Guideline VDI/VDE 3523 "Acceptance Test Guideline for Steam Turbine Control Systems". The extent to which this technical Guideline is to be applied and deemed to be mandatory shall be agreed upon between the parties to the contract; this also applies analogously to certain technical details in the practical conduct of the test and to the observance of agreed numerical values in connection with the acceptance test. The desirability and necessity to reach such agreement prior to the test is expressely pointed out in several places in this part of the Guideline. Another reason has been to allow for different engineering designs and duties of turbine plants and their connected consumers without unduly narrowing down and regularizing the latitude which this involves in choosing the test procedures.

The tests are intended to establish whether the turbine governing system meets the specified requirements. No numerical specifications have been included in this part of the Guideline; these should also be the subject of agreement between the parties to the contract (see in particular Section 4.1 of this Part 1).