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SEMI F50-0200 © SEMI 2000 7 factory and the electric utility at the point of common coupling (also kn own as the electrical service poin t). Many c ustom power option s include som e e nergy storage t o ride throu gh the…

SEMI F50-0200 © SEMI 2000 6

Impulse Insulation Levels

(BIL) are just some of the

ways that events can be eliminated.

6.4.3 Service Configurations

6.4.3.1 Determine the factors that are fixed for the

purposes of improvement development and evaluation.

Some examples include, but are not limited to, physical

location of site, utility system configuration beyond the

immediate vicinity of the site, and electric rate

structures.

6.4.3.2 Once the electrical reliability and power

quality needs of a semiconductor factory are identified

and the reliability and power quality of the electrical

network in the area has been characterized, electric

utility service configuration can be considered. The

electric utility and the semiconductor manufacturer

should jointly develop a plan that balances reliability

and power quality. This plan should consider the

following service configuration options.

6.4.3.3 High voltage service configura tions.

6.4.3.3.1 Utility electrical service configurations have

a significant effect on the levels of power quality and

reliability. Semiconductor manufacturing facilities can

typically derive the highest service quality and

reliability from electrical service provided at the highest

voltage level. By bringing service to the semiconductor

factory from the highest available voltage system,

semiconductor facilities can eliminate their exposure to

electrical disturbances on lower voltage systems.

Seldom are disturbances that result from events

originating in lower voltage systems transferred into the

higher voltage systems to any significant degree.

Utility industry studies have indicated approximately

60−75% fewer voltage sag events (below 70% of

nominal) on the high voltage systems.

6.4.3.3.2 For plants with loads greater than 10 MW,

the highest voltage available is usually service at a

voltage between 69 kV and 345 kV. Voltages above

this range, while widely used by utilities, are not

usually economical to adapt to loads less than 60 MW

and may require lengthy regulatory approvals. If new

overhead power lines are required, environmental and

public issues associated with locating the lines may

reduce access to higher voltage lines.

6.4.3.4 Redundancy.

6.4.3.4.1 All on-site facilities and internal factory

distribution should have at least N+1 component

redundancy. Where N is the number of components

required to operate for maximum loading conditions

and +1 indicates a single additional component that will

operate to maintain the system capability in the event

that one of the original components is out-of-service. If

the plant is to be operated with no annual shutdowns for

maintenance, then the system should be designed with

enough redundancy to maintain every component in the

plant without dropping service to any load. This

requires at least a dual feed system that originates with

two or more utility sources and continues throughout

the semiconductor factory with appropriate transfer

schemes to keep the loads energized at all times and to

transfer loads without interruptions.

6.4.3.4.2 The most reliable service is one where there

are multiple sources connected in a network to the

semiconductor factory. This allows for adequate power

supply, even if one of the sources fails. If a network is

not available, a dual feed system can be configured to

provide an immediate transfer to the backup system in

the case of primary source failure, reducing outage time

to near zero. Additionally, if the two sources are

independent, a static transfer switch may increase

quality to a level higher than that of a network. If only

one source is available to a semiconductor factory with

a load of less than five megawatts, an alternative is on

site generation combined with a voltage sag ride-

through system.

6.4.3.5 Minimize exposure.

6.4.3.5.1 When choosing source configurations, it is

important to consider exposure at the semiconductor

factory site. The more line length the factory is

connected to, the more exposure there is.

a) It might not be desirable to have three lines serving

the plant if one is a long line that is prone to

failures. As a rule of thumb, more than three lines

connected in a network may reduce quality without

adding significantly to reliability.

b) If service is taken from a distribution class circuit,

then consider purchasing a so-called express or

dedicated feeder from the utility to isolate the plant

from neighboring facilities.

c) Review the line routes with the utility and consider

changes to reduce exposures, such as: where the

poles are vulnerable to being struck by vehicles, or

where trees are growing close to the transmission

lines.

6.4.4 Power Enhancements Technologies

6.4.4.1 All disturbances will not be eliminated from

the utility grid. In order to achieve the next step in

plant protection, it may be necessary to implement

some type of custom power option. Custom power is

so called because it is thought to be a custom solution

tailored to the needs of the process and the unique

situation of the site. Custom power options usually

involve some type of power enhancement and

conditioning system. These power electronics systems

are most often connected between the semiconductor

SEMI F50-0200 © SEMI 20007

factory and the electric utility at the point of common

coupling (also known as the electrical service point).

Many custom power options include some energy

storage to ride through the disturbance, but they are

usually designed to carry the factory through only

momentary interruptions. In fact, for large factories

(>10 MW) some available ride-through systems only

operate to boost the voltage during sags and will not

carry the factory site through even short outages. The

trade-off is cost versus protection. The systems should

be economically evaluated as well as matched

technically to the needs of the site.

6.4.4.2 Electric utility provided custom power options

should be balanced against factory system voltage sag

immunity covered in industry guide for factory systems

voltage sag immunity.

6.5 Select and Implement Improvements

6.5.1 Both the electric utility and the semiconductor

manufacturer should agree criteria methodology for

prioritizing improvements. The following are examples

of prioritization criteria.

• Expected frequency of disturbances.

• Impact of fault on electric utility and

semiconductor processing.

• Relative cost of system improvement.

• Ability of action to reduce effects.

6.5.2 Select improvement to be implemented, identify

the schedules for installation, and define the new

system performance expectations.

6.5.3 Implement selected improvements.

6.5.4 With identified fault tracking and root cause

analysis processes electric utilities will be in a position

to communicate the cause of events, their corrective

actions, and the impact of improvements. Results will

be both immediate and long-term, but to ensure that the

continuous improvement process remains successful,

the impacts of improvements should be tracked. The

results of this tracking should provide feedback to the

continuous improvement process as a whole.

7 Related Documents

7.1 SEMI Standards

SEMI F42 — Test Method for Semiconductor

Processing Equipment Voltage Sag Immunity

SEMI F47 — Provisional Specification for

Semiconductor Processing Equipment Voltage Sag

Immunity

SEMI F49 — Guide for Semiconductor Factory

Systems Voltage Sag Immunity

SEMI E51 — Guide for Typical Facilities Services and

Termination Matrix

7.2 IEEE Standards

IEEE 141  IEEE Recommended Practice for Electric

Power Distribution for Industrial Plants

IEEE 446 — IEEE Recommended Practice for

Emergency and Standby Power Systems for Industrial

and Commercial Applications

IEEE 493 — IEEE Recommended Practice for the

Design of Reliable Industrial and Commercial Power

Systems

IEEE 1100 — IEEE Recommended Practice for

Powering and Grounding Sensitive Electronic

Equipment

IEEE 1250 — IEEE Guide for Service to Equipment

Sensitive to Momentary Voltage Disturbances

NOTE 3: As listed or revised, all documents cited shall be the

latest publications of adopted standards.

NOTICE: SEMI makes no warranties or

representations as to the suitability of the guides set

forth herein for any particular application. The

determination of the suitability of the guide is solely the

responsibility of the user. Users are cautioned to refer

to manufacturer’s instructions, product labels, product

data sheets, and other relevant literature respecting any

materials mentioned herein. These guides are subject to

change without notice.

The user’s attention is called to the possibility that

compliance with this guide may require use of

copyrighted material or of an invention covered by

patent rights. By publication of this guide, SEMI takes

no position respecting the validity of any patent rights

or copyrights asserted in connection with any item

mentioned in this guide. Users of this guide are

expressly advised that determination of any such patent

rights or copyrights, and the risk of infringement of

such rights, are entirely their own responsibility.

SEMI F50-0200 © SEMI 2000 8

RELATED INFORMATION 1

VOLTAGE SAG PERFORMANCE AT SEMICONDUCTOR FACTORY

SITES

NOTE: This related information is not an official part of

SEMI F50 and was derived from the work of the originating

task force. This related information was approved for

publication by full letter ballot procedures on December 15,

1999. Determination of the suitability of the material is solely

the responsibility of the user.

R1-1 Typical Electric Utility System

Performance

R1-1.1 Although most large semiconductor sites are

served from dedicated substations, data collected from

utility (medium-voltage) distribution circuits can be

useful in establishing a baseline for electric utility

system performance. As part of the EPRI*

Distribution Power Quality (DPQ) study, data was

collected for a two-year period from approximately 300

different BMI PQNode monitors. These monitors were

located on 100 different feeders at 24 geographically

dispersed utilities. The power quality database created

in conjunction with this study is probably the most

extensive in existence. The data derived from this

study provides a statistically based assessment of the

level of power quality on electric utility distribution

circuits (voltage range from 4.16kV to 34.5kV).

R1-1.2 Almost every category of power quality data

was collected in the DPQ study, however, only voltage

sag and interruption data is assumed to be pertinent to

this activity. In the DPQ study, a voltage sag event was

initiated when the rms voltage dropped below 95% of

nominal for one cycle (data analysis was performed

only for events with magnitudes less than or equal to

90%). An interruption event was initiated when the

voltage dropped below 10% of nominal for 120

seconds. Although waveforms were captured for most

sag and interruption events, almost all of the data

analysis was performed on the basis of minimum

voltage magnitude (as a percentage on nominal) and

maximum duration during the event.

R1-1.3 DPQ Key Results

• The average interruption rate per site, per month

was approximately 0.5.

• The average sag rate per site, per month was

approximately 4 (10% < V < = 90%).

• The ratio of voltage sags to interruptions was

approximately 10:1.

2 Electric Power Research Institute, Inc., 3412 Hillview Ave., Palo

Alto, CA 94304-1395, USA

• Almost all voltage sag events have only a single

component.

• Most voltage sags had duration of less than 10

cycles.

R1-1.4 The Figure R1-1 represents a summary of the

voltage sag and interruption data in a contour format.

The contour lines on the graph represent the expected

number of disturbance events that are more severe

(longer or deeper) than the duration and magnitude

grid.

R1-2 Semiconductor Factory Site Disturbance

Data

R1-2.1 The DPQ study provides a baseline of the

power quality that exists on typical utility distribution

systems. However, only one of the semiconductor

manufacturing sites from which data was collected is

served from a typical utility distribution system.

Fourteen of the fifteen semiconductor sites surveyed

were served from dedicated substations owned by either

the customer or the utility. A comparison between

DPQ and semiconductor site data (for large facilities)

indicates that application of DPQ data would yield a

more restrictive tool tolerance standard. It is

recommended, therefore, that data from semiconductor

sites be utilized to develop an initial curve and that the

curve be validated against DPQ data.

R1-2.2 Voltage sag and interruption data was

accumulated for 14 different semiconductor

manufacturing sites geographically dispersed

throughout the United States. One additional site was

located outside of the United States. Data represented

in this report was provided by semiconductor

manufacturing companies.

R1-2.3 All of the data collected was in the form of

magnitude and duration point values. Although the

validity of characterizing the electrical system

performance is this manner has been questioned, it

remains the most common data format for disturbance

data.

R1-2.4 The coverage of the disturbance data is

typically represented as the product of number of years

(or months) monitored and the number of monitors

present. In this report, the unit for data coverage is

Monitor-Years. One Monitor-Year of data is the

quantity of data derived by one monitor for a one-year

period. The data for semiconductor sites covers 30.5