API RP 17Z-2024
Medium Voltage Equipment Used on Subsea Production Systems

Standard No.

API RP 17Z-2024

Release Date

2024

Published By

American Petroleum Institute (API)  US  /  API

Introduction

Standard Overview

API RP 17Z provides recommended practices for medium-voltage equipment (3 kVac to 69 kVac) in underwater production systems, covering design, manufacture, testing, installation, and operation. This standard applies to single-phase and three-phase AC systems, excluding DC systems. The standard emphasizes considerations for the underwater environment, pressure compensation, and seawater intrusion.

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System Architecture Analysis

The standard provides four typical power supply topologies: single power string-top VSD, dual power string-top VSD, single power string-underwater VSD, and single power string-underwater distribution. These topologies are described in detail with single-line diagrams and require analysis of load current, short circuits, harmonics, etc.

Topology Type	VSD Location	Redundant Configuration	Typical Application
Single Power String - Top VSD	Above Water	No Redundancy	Simple Pump System
Dual Power String - Top VSD	Above Water	Redundant	High Reliability Applications
Single Power String - Underwater VSD	Underwater	No Redundancy	Long Distance Connection
Single Power Supply String - Underwater Power Distribution	Underwater	No Redundancy	Multiple Load Distribution

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Key Analysis Requirements

The standard requires the following analyses: load current, cable current carrying capacity, short circuit, protection coordination, stability, motor starting, harmonic analysis, transformer analysis, reliability, grounding, and switch transients. For example, harmonic analysis requires assessing total harmonic distortion (THD) and recommending filtering measures. The IEEE 3002 series of standards is recommended for specific analysis.

Case Study: Harmonic Analysis

A certain underwater booster project uses a VSD-driven underwater pump. Harmonic analysis revealed that the 5th and 7th harmonics exceeded the standard. An active power filter was subsequently installed, reducing the THD to below 5%.

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Test Requirements

The standard specifies Factory Test (FAT) and System Integration Test (SIT). SIT must simulate real-world operation, including motor start-up, stop sequence, fault protection, voltage regulation, dynamic testing, and long-term operation testing. Voltage, current, harmonics, and other parameters must be measured during the test.

Test Type	Purpose	Key Verification Points
FAT	Verify Single Device Functionality	Insulation Resistance, Communication, Leakage
SIT	Verify System Integration Functionality	Starting Torque, Protection Setting, Voltage Regulation
Extended FAT	Verify Multiple Interface Products	Joint Operation

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Implementation Recommendations

It is recommended to conduct a comprehensive system analysis and develop a detailed test plan early in the project. Pay special attention to the environmental adaptability of underwater equipment, such as pressure compensation and seawater intrusion monitoring. It is recommended to refer to API 17N for reliability management and follow IMCA D 045 guidelines for underwater electrical safety.

API RP 17Z-2024 Referenced Document

• IEC 60038 IEC standard voltages CONSOLIDATED EDITION

Standard and Specification