ISO 18888:2017

Gas turbine combined cycle power plants — Thermal performance tests

ISO 18888:2017 specifies standard rules for preparing, conducting, evaluating and reporting thermal performance tests on combined cycle and cogeneration power plants driven by gas turbines for base and part load operation with or without supplementary firing. ISO 18888:2017 is applicable to - thermal performance tests for general information, - thermal acceptance tests for determining the performance of the combined cycle plant in relation to a contractual guarantee, and - comparative tests designed to check the performance differentials of the combined cycle and cogeneration power plants, for testing before and after modifications, upgrades or overhauls. It can be used to determine the following thermal performance test goals and expected values, under specific operating and reference conditions within defined test boundaries: - electrical power output; - heat rate or thermal efficiency; - process steam and/or district heat w/o generation of electrical power output by means of a steam turbine. ISO 18888:2017 does not apply to individual equipment component testing, which is covered by corresponding standards. It is not intended to be applied to the following test goals: - environmental testing for example emissions, noise; - vibration testing; - operational testing; - absolute or comparative performance of specific components of the combined cycle covered by dedicated standards (e.g. gas turbines).

Turbines à gaz — Centrales à cycle combiné — Essais de performance thermique

General Information

• Status: Published
• Publication Date: 18-Oct-2017
• ICS: 27.040 - Gas and steam turbines. Steam engines
• ICS: 27.100 - Power stations in general
• Technical Committee: ISO/TC 192 - Gas turbines
• Drafting Committee: ISO/TC 192 - Gas turbines
• Parallel Committee: ISO/TC 67 - Materials, equipment and offshore structures for petroleum, petrochemical and natural gas industries
• Current Stage: 9093 - International Standard confirmed
• Completion Date: 11-Apr-2023

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 18888
First edition
2017-10
Gas turbine combined cycle power
plants — Thermal performance tests
Turbines à gaz — Centrales à cycle combiné — Essais de performance
thermique
Reference number
ISO 18888:2017(E)
©
ISO 2017

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ISO 18888:2017(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
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ISO 18888:2017(E)

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols and units . 6
5 Test boundary . 7
6 Preparation for test .11
6.1 General .11
6.2 Performance degradation .12
6.3 Measurement classification .12
6.4 Design and construction phase recommendations .12
6.5 Test procedure .13
6.6 Field preparations for the performance test .14
6.7 Instruments and measuring methods .16
6.7.1 General.16
6.7.2 Electrical power measurement .16
6.7.3 Flow measurements . .17
6.7.4 Temperature measurements .18
6.7.5 Relative humidity measurements .22
6.7.6 Pressure measurements .23
6.7.7 Data acquisition system .25
6.7.8 Wind velocity .25
6.7.9 Storage vessel levels .25
6.7.10 Data sampling .26
6.8 Determination of fuel properties .26
6.8.1 General.26
6.8.2 Tests on fuel gas .27
6.8.3 Tests on liquid fuel .27
6.9 Determination of cooling water flow into the condenser .28
6.9.1 General.28
6.9.2 Energy balance method .28
6.9.3 Cooling water pump performance curves .31
6.9.4 Direct flow measurement .32
6.10 Measurement uncertainties .32
6.11 Maximum allowable uncertainties .34
6.12 Calibration .35
7 Execution of test .36
7.1 Base reference conditions .36
7.1.1 General.36
7.1.2 Specified gaseous fuel.37
7.1.3 Specified liquid fuel .37
7.2 Preliminary test .38
7.3 Performance test .38
7.4 Duration of test runs .39
7.5 Auxiliary equipment operation.39
7.6 Tests with inlet air heating system .39
7.7 Tests with inlet air cooling system . .40
7.8 Maximum permissible variation in operation conditions .40
8 Calculation of results for absolute test .41
8.1 General .41
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ISO 18888:2017(E)

8.2 Correction to base reference conditions .41
8.2.1 General.41
8.2.2 Correction curves based correction approach .42
8.2.3 Thermodynamic heat balance model based correction approach.43
8.2.4 Boundary parameters for correction .44
8.2.5 Description of corrections to base reference conditions .46
8.3 Power output for combined cycle overall test .50
8.3.1 Measured power output .50
8.3.2 Power output corrected to nominal power factor .52
8.3.3 Corrected power output .52
8.4 Heat rate for combined cycle overall test .53
8.4.1 Measured heat rate/measured thermal efficiency .53
8.4.2 Corrected heat rate / corrected thermal efficiency .53
8.5 Power output of steam turbine determination for combined cycle in single
shaft configuration.54
9 Part load tests .54
9.1 General .54
9.2 Test set up and conduct .55
9.3 Correction method for part loads .57
10 Calculation of results for comparative test .57
10.1 General .57
10.2 Comparative performance test uncertainty .57
10.3 Preparation for comparative test .58
10.3.1 Instrumentation .58
10.3.2 Preliminary activities and plant settings .58
10.4 Execution of comparative tests and calculation of results .59
11 Test report .59
11.1 Form of the report .59
11.2 Detailed report .60
Annex A (informative) Typical secondary variables .61
Annex B (informative) Numerical examples of uncertainty calculation .64
Annex C (informative) Procedure for power factor conversion .69
Bibliography .73
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ISO 18888:2017(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 192, Gas turbines.
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ISO 18888:2017(E)

Introduction
This document specifies standard rules for preparing, conducting, evaluating and reporting thermal
performance tests in order to determine and/or verify the power output, the thermal efficiency (heat
rate) and/or other performance test parameters for gas turbine driven combined cycle power plants.
It provides information on methods of measurement considering uncertainties and on methods
for corrected results obtained under test conditions in order to compare to guaranteed or specified
conditions.
The objective of testing conducted per this document is to determine combined cycle thermal
performance characteristics in accordance with any previously drawn up agreements such as the
purchase agreements, test criteria documents, engineering, procurement and construction (EPC)
requirements, power purchase agreements, power and water purchase agreements, contractual
services agreements.
The document also provides guidelines for comparative tests designed to check performance
differentials of the combined cycle and cogeneration power plants, for testing before and after
modifications, upgrades or overhauls. Improvements to achieve additional performance of the combined
cycle may include modification/substitutions of main components and additions of components inside
test boundary. This comparative testing philosophy may also be used for “periodic testing” of the
plant in order to monitor overall plant performance degradation, while giving due consideration to the
relative testing uncertainty.
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INTERNATIONAL STANDARD ISO 18888:2017(E)
Gas turbine combined cycle power plants — Thermal
performance tests
1 Scope
This document specifies standard rules for preparing, conducting, evaluating and reporting thermal
performance tests on combined cycle and cogeneration power plants driven by gas turbines for base
and part load operation with or without supplementary firing.
This document is applicable to
— thermal performance tests for general information,
— thermal acceptance tests for determining the performance of the combined cycle plant in relation to
a contractual guarantee, and
— comparative tests designed to check the performance differentials of the combined cycle and
cogeneration power plants, for testing before and after modifications, upgrades or overhauls.
It can be used to determine the following thermal performance test goals and expected values, under
specific operating and reference conditions within defined test boundaries:
— electrical power output;
— heat rate or thermal efficiency;
— process steam and/or district heat w/o generation of electrical power output by means of a steam
turbine.
This document does not apply to individual equipment component testing, which is covered by
corresponding standards.
It is not intended to be applied to the following test goals:
— environmental testing for example emissions, noise;
— vibration testing;
— operational testing;
— absolute or comparative performance of specific components of the combined cycle covered by
dedicated standards (e.g. gas turbines).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 2314:2009, Gas turbines — Acceptance tests
ISO 3675, Crude petroleum and liquid petroleum products — Laboratory determination of density —
Hydrometer method
ISO 5167 (all parts), Measurement of fluid flow by means of pressure differential devices inserted in circular
cross-section conduits running in full
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ISO 18888:2017(E)

ISO 6974-1, Natural gas — Determination of composition and associated uncertainty by gas
chromatography — Part 1: General guidelines and calculation of composition
ISO 6975, Natural gas — Extended analysis — Gas-chromatographic method
ISO 6976, Natural gas — Calculation of calorific values, density, relative density and Wobbe indices from
composition
ISO 9951, Measurement of gas flow in closed conduits — Turbine meters
ISO 10715:1997, Natural gas — Sampling guidelines
ISO 10790, Measurement of fluid flow in closed conduits — Guidance to the selection, installation and use of
Coriolis flowmeters (mass flow, density and volume flow measurements)
ISO 12185, Crude petroleum and petroleum products — Determination of density — Oscillating U-tube
method
ISO 12213-2, Natural gas — Calculation of compression factor — Part 2: Calculation using molar-
composition analysis
ISO 17089-1, Measurement of fluid flow in closed conduits — Ultrasonic meters for gas — Part 1: Meters for
custody transfer and allocation measurement
ISO 20765-1, Natural gas — Calculation of thermodynamic properties — Part 1: Gas phase properties for
transmission and distribution applications
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
ASTM D1945, Standard Test Method for Analysis of Natural Gas by Gas Chromatography
ASTM D4052, Standard Test Method for Density, Relative Density, and API Gravity of Liquids by Digital
Density Meter
ASTM D4809, Standard Test Method for Heat of Combustion of Liquid Hydrocarbon Fuels by Bomb
Calorimeter
ASTM D4868, Standard Test Method for Estimation of Net and Gross Heat of Combustion of Burner and
Diesel Fuels
DIN 51900-1, Testing of solid and liquid fuels — Determination of gross calorific value by the bomb
calorimeter and calculation of net calorific value — Part 1: Principles, apparatus, methods
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1
absolute test
test carried out in order to prove an absolute guarantee or an absolute expected performance
3.2
comparative test
test carried out in order to prove a relative change or improvement of performance
EXAMPLE For retrofits.
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ISO 18888:2017(E)

3.3
performance test
means test of performance of power output, efficiency or heat rate, heat duty, process steam mass flows,
etc., as specified
EXAMPLE Performance tests could be specified in contractual agreements.
3.4
preliminary test
test or tests in advance of the actual performance test (3.3) to check the complete measuring system
and main components to verify that the power plant is in a suitable condition before conducting the
actual performance test
3.5
simple cycle
thermodynamic cycle consisting only of successive compression, combustion and expansion
Note 1 to entry: Generation of electrical power (3.16) output driven only from a gas turbine (3.29) or from the
gas turbine in combined cycle (3.28) using a bypass stack. The working fluid enters the gas turbine from the
atmosphere and is discharged into the atmosphere.
[SOURCE: ISO 11086:1996, 1.8, modified.]
3.6
open cycle
combined cycle (3.28) with the steam turbine bypassed in which the working fluid enters the gas
turbine from the atmosphere and is discharged through a heat recovery steam generator stack into the
atmosphere
Note 1 to entry: The generation of electrical power output in a combined cycle (3.28) plant operating in open cycle
is provided only from the gas turbine, as the steam turbine is bypassed.
3.7
test boundary
imaginary boundary drawn encompassing the major equipment included in the test scope
3.8
heat duty
thermal net/gross output produced from the combined cycle (3.28) plant
3.9
heat rate
HR
ratio of the fuel energy supplied per unit time to the electrical power produced
Note 1 to entry: Inverse of thermal efficiency.
Note 2 to entry: The heat rate is expressed in units of kilojoules per kilowatt hour.
[SOURCE: ISO 11086:1996, 5.31, modified.]
3.10
heating value
calorific value
specific energy
amount of heat released by the complete combustion in air of a specific quantity of gas or liquid fuel
when the reaction takes place at constant pressure
Note 1 to entry: If the combustion products accounted for are only in the gaseous state, the value is called lower
heating value (LHV) or inferior calorific value or net heating value. If the combustion products are gaseous with
the exception of water, which is in liquid state, the value is called higher heating value (HHV) or superior calorific
value or gross heating value at 15 °C for natural gas fuel.
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ISO 18888:2017(E)

Note 2 to entry: HHV at constant volume and a reference temperature of 15 °C shall be determined by means of a
bomb calorimeter method. Then LHV at constant volume is found by calculation deducting the latent heat of the
calculated amount of water vapour produced from the measured hydrogen content of the fuel.
3.11
high pressure
HP
highest pressure level of the working fluid
3.12
intermediate pressure
IP
medium pressure level of the working fluid
3.13
low pressure
LP
lowest pressure level of the working fluid
3.14
mechanical loss
reduction of power output due to bearing and windage losses of gas and steam turbine rotors
[SOURCE: ISO 11086:1996 5.34, modified.]
3.15
hot water
host that can accept or supply energy (non-fuel) to a cycle
3.16
power
quantity expressed in terms of mechanical shaft power at the turbine coupling or electrical power of
the turbine-generator
3.17
primary variable
value that is measured and used for calculation and correction of test results
3.18
process steam
host that can accept or supply energy (non-fuel) to the cycle
EXAMPLE District heating, steam consumers (refinery, pulp and paper industries, petrochemical industries),
steam producers (auxiliary boilers, steam from other power plant blocks), etc.
3.19
secondary variable
value that is measured but that will not be used for calculation of the results
Note 1 to entry: These variables are measured to ensure that the required test conditions are not violated and to
provide information for future use.
3.20
standard reference condition
condition for the ambient air or intake air at the compressor flange (alternatively, the compressor
intake flare) equal to
— absolute pressure of 101,325 kPa (1,01325 bar; 760 mmHg),
— temperature of 15 °C, and
— relative humidity of 60 %
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Note 1 to entry: The conditions are defined in ISO 2533.
Note 2 to entry: In the case of the closed cycle, the standard conditions for the air heater are 15 °C and 101,325 kPa
for the ambient atmospheric air.
Note 3 to entry: An inlet water temperature of 15 °C applies if cooling of the working fluid is used.
Note 4 to entry: These reference conditions may be different if otherwise agreed in contractual documents or
agreements.
3.21
thermal efficiency
ratio of electrical power (3.16) output to the heat consumption
Note 1 to entry: Inverse of heat rate.
Note 2 to entry: It can be based on lower or higher heating value.
[SOURCE: ISO 3977-1:1997, 2.3.4, modified.]
...